The present disclosure relates to telecommunications apparatus and methods. In particular,
certain embodiments relate to apparatus and methods for determining the height (i.e. altitude /
elevation) of a terminal device operating in a wireless telecommunications system.
Description of Related Art
The "background" description provided herein is for the purpose of generally presenting the
context of the disclosure. Work of the presently named inventor, to the extent it is described in
this background section, as well as aspects of the description which may not otherwise qualify
as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against
the present invention.
Mobile communication systems have evolved over the past ten years or so from the GSM
System (Global System for Mobile communications) to the 3G system and now include packet
data communications as well as circuit switched communications. The third generation
partnership project (3GPP) has developed a fourth generation mobile communication system
referred to as Long Term Evolution (LTE) in which a core network part has been evolved to form
a more simplified architecture based on a merging of components of earlier mobile radio
network architectures and a radio access interface which is based on Orthogonal Frequency
Division Multiplexing (OFDM) on the downlink and Single Carrier Frequency Division Multiple
Access (SC-FDMA) on the uplink. Further developments to LTE-based systems are being made
in the context of so-called Long Term Evolution - Advanced (LTE-A) architectures.
Newer generations of mobile telecommunication systems, such as those based on the 3GPP
defined UMTS and Long Term Evolution (LTE) (including LTE-A) architectures are able to
support more sophisticated services than simple voice and messaging services offered by
previous generations of mobile telecommunication systems. This has led to the development of
terminal devices, such as so-called smart phones, that are able to provide functionality that
goes beyond simple voice and messaging services. One aspect of terminal devices that is
becoming more and more common is the ability for terminal devices to determine their own
location, for example using satellite-based positioning systems, such as the Global Positioning
Satellite (GPS) system. Other satellite-based positioning systems could be used, such as the
Galileo system and the Global Navigation Satellite System (GLONASS).
There have been proposals to make use of terminal device's ability to establish and report its
location for various purposes, for example to help locate a lost telephone or to help emergency
responders locate a person needing assistance. With this in mind, in the United States of
America the Federal Communications Commission (FCC) has issued a proposal to the mobile
industry to seek to provide schemes for locating terminal devices with sufficient accuracy to
allow emergency responders to more reliably locate a terminal device in a building (see FCC
publication FCC-14-13, Wireless E91 1 Location Accuracy Requirements, PS Docket No. 07-
114, Adopted: February 20, 2014 Released: February 2 1, 2014 -
https://apps.fcc.gov/edocs_public/attachmatch/FCC-14-13A1 .pdf [1]).
It may be expected existing schemes for determining a terminal device's location, for example
using a GPS receiver in the terminal device (potentially with assistance from other positioning
technologies, such as Wi-Fi and / or cellular positioning techniques using so-called assisted
GPS), may already be able to provide a desired level of positioning accuracy in horizontal
dimensions (i.e. to provide a 2D position, e.g. in terms of latitude and longitude). However, it is
well recognized that GPS-based receivers are typically less accurate when providing height
information. This is basically because a GPS receiver can only receive signals from satellites
above the horizon, whereas for each direction in the horizontal plane they can receive signalling
from satellites located to both sides of the receiver. Consequently, it can be expected that
existing schemes for determining a terminal device's position may be unable to determine the
location of a terminal device with sufficient vertical accuracy to allow the floor of a building in
which the terminal device is located to be reliably determined. The issue of reduced vertical
accuracy as compared to horizontal accuracy is especially significant in the context of seeking
to determine on which floor of a building a terminal device is located because GPS-based
receivers generally work less well in buildings due to increased signal penetration losses.
Furthermore, the consequence of an inaccurate height determination will often be more
significant than an inaccurate horizontal position because it will generally take an emergency
responder more time to move from one floor to another floor when it is realised there is an error
in vertical determination than to move from one room to another room on the same floor when
there is an error in horizontal determination.
In view of these issues there is a need for improved schemes for determining the height (vertical
location) of a terminal device operating in a wireless telecommunications system.
SUMMARY
According to a first aspect of the present disclosure, there is provided a method of determining
an altitude of a terminal device operating in a wireless telecommunications network comprising
the terminal device, and another network entity, the method comprising: measuring, by the
terminal device, an indication of barometric pressure in the vicinity of the terminal device;
establishing, at the other network entity, calibration information for the indication of barometric
pressure measured at the terminal device; and determining the altitude of the terminal device
from the indication of barometric pressure measured by the terminal device and the calibration
information established at the other network entity.
According to a second aspect of the present disclosure, there is provided a wireless
telecommunications network, comprising: a terminal device configured to measure an indication
of barometric pressure at the terminal device; and another network entity configured to establish
calibration information for the indication of barometric pressure measured at the terminal device,
wherein at least one of the terminal device and the other network entity is configured to
determine an indication of an altitude of the terminal device from the indication of barometric
pressure measured at the terminal device and the calibration information established at the
other network entity.
According to a third aspect of the present disclosure, there is provided a method of operating a
terminal device in a wireless telecommunications network to determine an altitude for the
terminal device; the method comprising: measuring an indication of barometric pressure at the
terminal device; receiving calibration information for the indication of barometric pressure
measured at the terminal device from another network entity; and determining the altitude of the
terminal device from the indication of barometric pressure measured at the terminal device and
the calibration information received from the other network entity.
According to a fourth aspect of the present disclosure, there is provided a terminal device
comprising: a pressure sensor configured to measure an indication of barometric pressure; a
transceiver unit configured to receive calibration information for the indication of barometric
pressure measured by the terminal device from another network entity; and a controller unit
configured to determine an indication of an altitude of the terminal device from the indication of
barometric pressure measured by the terminal device and the calibration information received
from the other network entity.
According to a fifth aspect of the present disclosure, there is provided circuitry for a terminal
device comprising a controller element and a transceiver element configured to operate
together to: obtain an indication of a measurement of barometric pressure made by the terminal
device; receive calibration information for the indication of the measurement of barometric
pressure made by the terminal device from another network entity; and determine an indication
of an altitude of the terminal device from the indication of a measurement of barometric
pressure made by the terminal device and the calibration information received from the other
network entity.
According to a sixth aspect of the present disclosure, there is provided a method of operating a
base station in a wireless telecommunications network to determine an altitude for a terminal
device; the method comprising: receiving from the terminal device an indication of a
measurement of barometric pressure made by the terminal device; establishing calibration
information for the indication of the measurement of barometric pressure made by the terminal
device; and determining an indication of an altitude of the terminal device from the indication of
the measurement of barometric pressure made by the terminal device and the calibration
information established by the base station.
According to a seventh aspect of the present disclosure, there is provided a base station
comprising: a transceiver unit configured to receive from a terminal device an indication of a
measurement of barometric pressure made by the terminal device; a calibration information
generation unit configured to establish calibration information for the indication of the
measurement of barometric pressure made by the terminal device; and a controller unit
configured to determine an indication of an altitude of the terminal device from the indication of
the measurement of barometric pressure made by the terminal device and the calibration
information established by the base station.
According to an eighth aspect of the present disclosure, there is provided circuitry for a base
station comprising a controller element and a transceiver element configured to operate
together to: receive from the terminal device an indication of a measurement of barometric
pressure made by the terminal device; establish calibration information for the indication of the
measurement of barometric pressure made by the terminal device; and determine an indication
of an altitude of the terminal device from the indication of the measurement of barometric
pressure made by the terminal device and the calibration information established by the base
station.
Further respective aspects and features are defined by the appended claims.
The foregoing paragraphs have been provided by way of general introduction, and are not
intended to limit the scope of the following claims. The described embodiments, together with
further advantages, will be best understood by reference to the following detailed description
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the disclosure and many of the attendant advantages thereof
will be readily obtained as the same becomes better understood by reference to the following
detailed description when considered in connection with the accompanying drawings wherein
like reference numerals designate identical or corresponding parts throughout the several
views, and wherein:
Figure 1 provides a schematic diagram illustrating an example of a mobile telecommunication
system;
Figure 2 provides a schematic diagram illustrating a LTE radio frame;
Figure 3 provides a schematic diagram illustrating an example of a LTE downlink radio
subframe;
Figure 4 schematically represents a wireless telecommunications system according to an
embodiment of the disclosure;
Figure 5 is a ladder diagram schematically representing methods of operation in accordance
with certain embodiments of the disclosure; and
Figure 6 is a ladder diagram schematically representing methods of operation in accordance
with certain other embodiments of the disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Figure 1 provides a schematic diagram illustrating some basic functionality of a mobile
telecommunications network / system 100 operating in accordance with LTE principles and
which may be adapted to implement embodiments of the disclosure as described further below.
Various elements of Figure 1 and their respective modes of operation are well-known and
defined in the relevant standards administered by the 3GPP (RTM) body and also described in
many books on the subject, for example, Holma H. and Toskala A [2]. It will be appreciated that
operational aspects of the telecommunications network which are not specifically described
below may be implemented in accordance with any known techniques, for example according to
the relevant standards.
The network 100 includes a plurality of base stations 101 connected to a core network 102.
Each base station provides a coverage area 103 (i.e. a cell) within which data can be
communicated to and from terminal devices 104. Data is transmitted from base stations 10 1 to
terminal devices 104 within their respective coverage areas 103 via a radio downlink. Data is
transmitted from terminal devices 104 to the base stations 101 via a radio uplink. The core
network 102 routes data to and from the terminal devices 104 via the respective base stations
101 and provides functions such as authentication, mobility management, charging and so on.
Terminal devices may also be referred to as mobile stations, user equipment (UE), user
terminal, mobile radio, and so forth. Base stations may also be referred to as transceiver
stations / nodeBs / e-nodeBs, and so forth.
Mobile telecommunications systems such as those arranged in accordance with the 3GPP
defined Long Term Evolution (LTE) architecture use an orthogonal frequency division
modulation (OFDM) based interface for the radio downlink (so-called OFDMA) and a single
carrier frequency division multiple access scheme (SC-FDMA) on the radio uplink. Figure 2
shows a schematic diagram illustrating an OFDM based LTE downlink radio frame 201 . The
LTE downlink radio frame is transmitted from a LTE base station (known as an enhanced Node
B) and lasts 10 ms. The downlink radio frame comprises ten subframes, each subframe lasting
1 ms. A primary synchronisation signal (PSS) and a secondary synchronisation signal (SSS)
are transmitted in the first and sixth subframes of the LTE frame. A physical broadcast channel
(PBCH) is transmitted in the first subframe of the LTE frame.
Figure 3 is a schematic diagram of a grid which illustrates the structure of an example
conventional downlink LTE subframe. The subframe comprises a predetermined number of
symbols which are transmitted over a 1ms period. Each symbol comprises a predetermined
number of orthogonal subcarriers distributed across the bandwidth of the downlink radio carrier.
The example subframe shown in Figure 3 comprises 14 symbols and 1200 subcarriers spread
across a 20MHz bandwidth and in this example is the first subframe in a frame (hence it
contains PBCH). The smallest allocation of physical resource for transmission in LTE is a
resource block comprising twelve subcarriers transmitted over one subframe. For clarity, in
Figure 3, each individual resource element is not shown, instead each individual box in the
subframe grid corresponds to twelve subcarriers transmitted on one symbol.
Figure 3 shows in hatching resource allocations for four LTE terminals 340, 341 , 342, 343. For
example, the resource allocation 342 for a first LTE terminal (UE 1) extends over five blocks of
twelve subcarriers (i.e. 60 subcarriers), the resource allocation 343 for a second LTE terminal
(UE2) extends over six blocks of twelve subcarriers (i.e. 72 subcarriers), and so on.
Control channel data can be transmitted in a control region 300 (indicated by dotted-shading in
Figure 3) of the subframe comprising the first "n" symbols of the subframe where "n" can vary
between one and three symbols for channel bandwidths of 3MHz or greater and where "n" can
vary between two and four symbols for a channel bandwidth of 1.4MHz. For the sake of
providing a concrete example, the following description relates to host carriers with a channel
bandwidth of 3MHz or greater so the maximum value of "n" will be 3 (as in the example of
Figure 3). The data transmitted in the control region 300 includes data transmitted on the
physical downlink control channel (PDCCH), the physical control format indicator channel
(PCFICH) and the physical HARQ indicator channel (PHICH). These channels transmit physical
layer control information. Control channel data can also or alternatively be transmitted in a
second region of the subframe comprising a number of subcarriers for a time substantially
equivalent to the duration of the subframe, or substantially equivalent to the duration of the
subframe remaining after the "n" symbols. The data transmitted in this second region is
transmitted on the enhanced physical downlink control channel (EPDCCH). This channel
transmits physical layer control information which may be in addition to that transmitted on other
physical layer control channels.
PDCCH and EPDCCH contain control data indicating which subcarriers of the subframe have
been allocated to specific terminals (or all terminals or subset of terminals). This may be
referred to as physical-layer control signalling / data. Thus, the PDCCH and/or EPDCCH data
transmitted in the control region 300 of the subframe shown in Figure 3 would indicate that UE1
has been allocated the block of resources identified by reference numeral 342, that UE2 has
been allocated the block of resources identified by reference numeral 343, and so on.
PCFICH contains control data indicating the size of the control region (i.e. between one and
three symbols for channel bandwidths of 3 MHz or greater and between two and four symbols
for channel bandwidths of 1.4 MHz).
PHICH contains HARQ (Hybrid Automatic Request) data indicating whether or not previously
transmitted uplink data has been successfully received by the network.
Symbols in a central band 310 of the time-frequency resource grid are used for the transmission
of information including the primary synchronisation signal (PSS), the secondary
synchronisation signal (SSS) and the physical broadcast channel (PBCH). This central band
310 is typically 72 subcarriers wide (corresponding to a transmission bandwidth of 1.08 MHz).
The PSS and SSS are synchronisation signals that once detected allow a LTE terminal device
to achieve frame synchronisation and determine the physical layer cell identity of the enhanced
Node B transmitting the downlink signal. The PBCH carries information about the cell,
comprising a master information block (MIB) that includes parameters that LTE terminals use to
properly access the cell. Data transmitted to terminals on the physical downlink shared channel
(PDSCH), which may also be referred to as a downlink data channel, can be transmitted in
other resource elements of the subframe. In general PDSCH conveys a combination of userplane
data and non-physical layer control-plane data (such as Radio Resource Control (RRC)
and Non Access Stratum (NAS) signalling ) . The user-plane data and non-physical layer
control-plane data conveyed on PDSCH may be referred to as higher layer data (i.e. data
associated with a layer higher than the physical layer).
Figure 3 also shows a region of PDSCH containing system information and extending over a
bandwidth of R344. A conventional LTE subframe will also include reference signals which are
discussed further below but not shown in Figure 3 in the interests of clarity.
The number of subcarriers in a LTE channel can vary depending on the configuration of the
transmission network. Typically this variation is from 72 sub carriers contained within a 1.4MHz
channel bandwidth to 1200 subcarriers contained within a 20MHz channel bandwidth (as
schematically shown in Figure 3). As is known in the art, data transmitted on the PDCCH,
PCFICH and PHICH is typically distributed on the subcarriers across the entire bandwidth of the
subframe to provide for frequency diversity. Therefore a conventional LTE terminal must be able
to receive the entire channel bandwidth in order to receive and decode the control region.
As explained above, in a LTE subframe the PDSCH generally occupies groups of resource
elements which follow the control region. The data in the blocks of resource elements 340, 341 ,
342, 343 allocated to the different mobile communication terminals (UEs) and the system
information data in the block of resources 344 shown in Figure 3 have a smaller bandwidth than
the bandwidth of the entire carrier. To decode these blocks a terminal first receives the PDCCH
spread across the frequency range R320 and/or the EPDCCH to determine if the (E)PDCCH
indicates there are PDSCH resources in the subframe that need to be decoded by the UE. The
intended recipient(s) for (E)PDCCH signalling in LTE is established through the use of radio
network temporary identifiers (RNTI). (E)PDCCH signalling is addressed to a particular RNTI by
using the RNTI to scramble cyclic redundancy check (CRC) bits associated with the (E)PDCCH
signalling. Each connected UE in a cell is associated with a Cell RNTI (C-RNTI) that may be
used to address PDCCH signalling to that particular UE. In addition there are other RNTIs
defined and these may be used to simultaneously address groups of terminal devices. For
example, a System Information RNTI (SI-RNTI) is defined and PDSCH transmissions
comprising SI are allocated by (E)PDCCH signalling addressed to SI-RNTI. Various other
RNTIs are defined for various other types of signalling. Some examples include a randomaccess
RNTI (RA-RNTI), a Paging RNTI (P-RNTI), a Transmit Power Control Physical Uplink
Control Channel RNTI (TPC-PUCCH-RNTI) and a Transmit Power Control Physical Uplink
Shared Channel-RNTI (TPC-PUSCH-RNTI).
Thus, once a UE has received a downlink subframe, the UE searches for (E)PDCCH signalling
associated with any RNTI that apply for the UE in the subframe to identify any corresponding
allocations of transmission resources on PDSCH. If there is an allocation message addressed
to the UE on (E)PDCCH the UE will proceed to decode the PDSCH in the relevant frequency
range (if any) indicated by the PDCCH. So for example, UE 1 discussed above decodes the
whole control region 300 to determine its resource allocation and then extracts the relevant data
from the corresponding resource block 342.
Figure 4 schematically shows a telecommunications system 400 according to an embodiment of
the disclosure. The telecommunications system 400 in this example is based broadly on a LTEtype
architecture. As such many aspects of the operation of the telecommunications system 400
are standard and well understood and not described here in detail in the interest of brevity.
Operational aspects of the telecommunications system 400 which are not specifically described
herein may be implemented in accordance with any known techniques, for example according
to the established LTE-standards and known variations thereof.
The telecommunications system 400 comprises a core network part (evolved packet core) 402
coupled to a radio network part. The radio network part comprises a base station (evolvednodeB)
404 and a terminal device 420. It will of course be appreciated that in practice the radio
network part may comprise a plurality of base stations serving a larger number of terminal
devices across various communication cells. However, only a single base station and terminal
device are shown in Figure 4 in the interests of simplicity.
As with a conventional mobile radio network, the terminal device 420 is arranged to wirelessly
communicate data to and from the base station (transceiver station) 404. The base station is in
turn communicatively connected to a serving gateway, S-GW, (not shown) in the core network
part which is arranged to perform routing and management of mobile communications services
to and from the terminal device 420 in the telecommunications system 400 via the base station
404. In order to maintain mobility management and connectivity, the core network part 402 also
includes a mobility management entity (not shown) which manages the enhanced packet
service, EPS, connections with terminal devices, such as terminal device 420, operating in the
communications system based on subscriber information stored in a home subscriber server,
HSS. Other network components in the core network (also not shown for simplicity) include a
policy charging and resource function, PCRF, and a packet data network gateway, PDN-GW,
which provides a connection from the core network part 402 to an external packet data network,
for example the Internet. As noted above, the operation of the various elements of the
communications system 400 shown in Figure 4 may be broadly conventional apart from where
modified to provide functionality in accordance with embodiments of the disclosure as discussed
herein.
The terminal device 420 comprises a transceiver unit 422 for transmission and reception of
wireless signals and a controller unit 424 configured to control the operation of the terminal
device 420 in accordance with embodiments of the disclosure. The controller unit 424
comprises a processor unit which is suitably configured / programmed to provide the desired
functionality described herein using conventional programming / configuration techniques for
equipment in wireless telecommunications systems. The transceiver unit 422 and controller unit
424 are schematically shown in Figure 4 as separate elements within terminal device 420 for
ease of representation. However, it will be appreciated the functionality of these units can be
provided in various different ways, for example using a single suitably programmed general
purpose computer, or suitably configured application-specific integrated circuit(s) / circuitry, or
using a plurality of discrete circuitry / processing elements for providing different elements of the
desired functionality. It will be appreciated the terminal device 420 will in general comprise
various other elements associated with its operating functionality in accordance with established
wireless telecommunications techniques (e.g. a power source, possibly a user interface, and so
forth).
As has become commonplace in the field of wireless telecommunications, terminal devices may
support Wi-Fi and Bluetooth functionality in addition to cellular / mobile telecommunications
functionality. Thus the transceiver unit 422 of the respective terminal device may comprise
functional modules operable according to different wireless communications operating
standards. For example, the terminal devices' transceiver units may each comprise an LTE
transceiver module for supporting wireless communications in accordance with an LTE-based
operating standard, a WLAN transceiver module for supporting wireless communications in
accordance with a WLAN operating standard (e.g. a Wi-Fi standard), and a Bluetooth
transceiver module for supporting wireless communications in accordance with a Bluetooth
operating standard. The underlying functionality of the different transceiver modules may be
provided in accordance with conventional techniques. For example, a terminal device may have
separate hardware elements to provide the functionality of each transceiver module, or
alternatively, a terminal device might comprise at least some hardware elements which are
configurable to provide some or all functionality of multiple transceiver modules. Thus the
transceiver unit 422 of the terminal device 420 represented in Figure 4 is assumed here to
provide the functionality of an LTE transceiver module, a Wi-Fi transceiver module and a
Bluetooth transceiver module in accordance with conventional wireless communications
techniques.
In addition to these elements, the terminal device 420 operating in accordance with
embodiments of the disclosure comprises a GPS module 426 and a pressure sensor 428. The
GPS module 426 is operable in conjunction with the controller unit 424 to establish a position of
the terminal device from signals received from GPS satellites in accordance with conventional
techniques. The pressure sensor 428 (which may also be referred herein to as a barometer) is
configured in conjunction with the controller unit 424 to establish a measurement of atmospheric
/ barometric pressure at the terminal device 420. The pressure sensor 428 may be based on
any established techniques for sensing atmospheric pressure and may be controlled by the
controller unit 424 to undertake measurements of barometric pressure and to provide an
indication of measured pressures to the controller unit 424 in accordance with generally
conventional sensor techniques.
In this example the barometer 428 is based on a solid-state barometer, such as the BMP1 80
digital barometric pressure sensor from Bosch Sensortec - http://www.boschsensortecxom/
en_GB/homepage/products_3/environmental_sensors_1/bmp180_1/bmp180 [3],
the BMP280 barometric pressure sensor from Bosch Sensortec - http://www.boschsensortec.
com/en_GB/homepage/products_3/environmental_sensors_1/bmp280/bmp280 [4], or
the BME280 integrated environmental sensor from Bosch Sensortec - http://www.boschsensortec.
com/en_GB/homepage/products_3/environmental_sensors_1/bme280/bme280_1 [5].
However, other types of "off the shelf" barometer could equally be used in accordance with
other examples of the disclosure.
The base station 404 comprises a transceiver unit 406 for transmission and reception of
wireless signals and a controller unit 408 configured to control the base station 404. The
controller unit 408 may comprise a processor unit which is suitably configured / programmed to
provide the desired functionality described herein using conventional programming /
configuration techniques for equipment in wireless telecommunications systems. The
transceiver unit 406 and the controller unit 408 are schematically shown in Figure 4 as separate
elements for ease of representation. However, it will be appreciated that the functionality of
these units can be provided in various different ways, for example using a single suitably
programmed general purpose computer, or suitably configured application-specific integrated
circuit(s) / circuitry or using a plurality of discrete circuitry / processing elements for providing
different elements of the desired functionality. It will be appreciated the base station 404 will in
general comprise various other elements associated with its operating functionality. For
example, the base station 404 will in general comprise a scheduling entity responsible for
scheduling communications. The functionality of the scheduling entity may, for example, be
subsumed by the controller unit 408.
In addition to these elements, the base station 404 comprises a calibration information
generator unit 410 for generating calibration information to be used for calibrating pressure
measurements from the pressure sensor 428 of the terminal device 420 as described further
herein. The calibration information generator unit 410 may generate different kinds of
information in accordance with different embodiments of the disclosure as described further
below. In this example the calibration information generator unit 4 10 is a pressure sensor
(barometer) configured in conjunction with the controller unit 408 of the base station 404 to
establish measurements of atmospheric / barometric pressure at the base station 404. As for
the pressure sensor 428 of the terminal device 420, the pressure sensor 4 10 of the base station
404 may be based on any established techniques for sensing atmospheric pressure and may
again be controlled by the controller unit 408 to undertake measurements of barometric
pressure and to provide an indication of measured pressures to the controller unit 404 in
accordance with generally conventional sensor techniques. Thus the calibration information
generator unit 410 of the base station may again comprise a solid-state barometer, such as the
BMP180 [3], BMP280 [4], or the BME280 [5] referred to above. However, any other "off the
shelf" barometer technology could equally be used.
Thus, the base station 404 and the terminal device 420 are both operable to measure the air
pressure in their vicinity (local air pressure) using their respective pressure sensors 4 10, 428.
The base station 404 and terminal device 420 are also operable to communicate data with one
another over a wireless (radio) communication link 4 18 in accordance with the established
practices of wireless (cellular) telecommunications systems.
As noted above, there is a need for improved schemes for determining the height (vertical
location / altitude) of a terminal device operating in a wireless telecommunications system. The
Inventor has recognized that providing a terminal device with a pressure sensor (barometer)
can help with determining the terminal device's height (i.e. its vertical offset from a reference
location, such as sea level). It is known that barometers (atmospheric pressure sensors) can be
used to provide height information and pressure sensors for measuring atmospheric pressure
are available which are suitable for incorporation in terminal devices, such as smartphones [3],
[4], [5]. However the relationship between atmospheric pressure (e.g. as measured by a
barometer) and height depends on climactic conditions, and this means a simple measurement
of atmospheric pressure in the vicinity of a terminal device may not be able to identify the height
of the terminal device with a desired level of accuracy.
Air pressure typically falls exponentially with increasing height and there are various models for
how pressure varies with height. One recognized model (barometric formula) for the variation in
pressure (P) with height (h) for an isothermal atmosphere is provided by the equation:
Equation 1: P h =
where P0 is the pressure at a reference height, commonly taken to be sea level, P(h) is the
pressure at a height h above the reference height, M is the molar mass of Earth's air (which
may be taken to be around 0.0290 kg mol 1) , g is the acceleration due to gravity (9.81 m s 2) , R
is the molar gas constant (8.31 m2 kg s 2 K 1 mol 1) , and T is the temperature of the atmosphere
(typically on the order of 290 K).
Another recognized model for the variation in pressure (P) with height (h) applicable for a nonisothermal
atmosphere (i.e. an atmosphere in which temperature falls with height) is provided
by the equation:
-Mg/RL
Equation 2
where again P0 is the pressure at a reference height, commonly taken to be sea level, P(h) is
the pressure at a height h above the reference height, M is the molar mass of Earth's air
(around 0.0290 kg mol 1) , g is the acceleration due to gravity (9.81 m s 2) , R is the molar gas
constant (8.31 m2 kg s~2 K 1 mol 1 ) , T0 is the temperature of the atmosphere at the reference
height (typically on the order of 290 K) and L is the temperature lapse rate (typically around 6.5
x 10 3 K m 1) .
Various other barometric formulae are known, for example although Equation 2 uses the
temperature of the atmosphere at the reference height, it can be readily reformulated to use the
temperature T at the height h by in effect by replacing T0 with T + Lh.
An issue with using such barometric formulae to establish the height of a terminal device from a
measure of barometric pressure made at the terminal device is the pressure at a given height
above a reference level / altitude (e.g. sea level) scales linearly with the pressure at the
reference point, can vary with changing climatic conditions. For example, assuming a sea-level
pressure of 1000 mbar (equivalent to 1000 hPa) and assuming a uniform temperature of around
290 K in the lower atmosphere, a pressure measurement of around 1010 mbar corresponds
with a height of around 100 m above sea level. However, if the pressure at sea level were to
change by 1 mbar, for example due to changing weather conditions, a pressure measurement
of 1010 mbar would correspond to a height of around 90 meters. Thus, a change in pressure at
sea level of 1 mbar has the same effect on a measured pressure as a 10 m change in the
height at which the pressure is measured. It is not uncommon for air pressure to change by 10
mbar during a day, and without taking account of this change, corresponding estimates of
altitude based on pressure measurements at a fixed height may vary by 100 m or so.
Therefore to more reliably estimate an altitude of a terminal device from a measurement of the
air pressure in the vicinity of the terminal device, the measurement should be calibrated using
calibration information, which might comprise an indication of a reference pressure at a
reference altitude, for example an indication of pressure at sea level. The terminal device may
then determine its height relative to the reference altitude (e.g. sea level) based on the
difference between the air pressure measured at the terminal device and the reference air
pressure (e.g. the pressure at sea level) using any of the established barometric formulae. In
general the most appropriate barometric formula (relationship between pressure and height)
may be selected according to the situation at hand. For example, it may be expected that
terminal devices will generally be operating at heights of less than 1 km, and so and so a
barometric formula that is considered to be most accurate in this regime of the atmosphere may
be used (for example as compared to one considered appropriate for altitudes relevant for
aircraft). Thus the specific barometric formula adopted may be based on any known models for
pressure variation with height.
In view of the above, the Inventor has recognized the importance of using calibration
information when seeking to determine the altitude of a terminal device from a pressure
measurement made by the terminal device. Furthermore, the Inventor has recognized how a
base station can be used to establish appropriate calibration information, for example an
indication of a reference barometric pressure for a reference altitude.
Figure 5 is a ladder diagram schematically representing modes of operation of the base station
404 and the terminal device 420 represented in Figure 4 in accordance with some embodiments
of the disclosure.
The processing begins in step S 1 in which the terminal device determines that a height estimate
should be made. The reason why the terminal device has determined a height estimate should
be made is not significant. For example, in some implementations the terminal device may be
configured to determine its height according to a regular schedule. In other implementations, the
terminal device may be configured to determine its height in response to a user input. For
example, the user may place an emergency call and the terminal device may be configured to
automatically determine its height in response to this (i.e. so it can be reported to an emergency
responder). In other implementations, the terminal device may be configured to determine its
height in response to signaling received from a base station instructing the terminal device to do
so.
In general, it may be expected that in step S 1 the terminal device will in fact determine that a full
3D position estimate should be made (i.e. including horizontal position information, such as
latitude and longitude, as well as height information / altitude information). However, it is
assumed here the horizontal positioning information is established using conventional means,
for example using GPS techniques, possibly with assistance from other positioning
technologies, such as those using wireless LAN (Wi-Fi) and/or Bluetooth (e.g. iBeacon)
signaling. However, since it is assumed here the terminal device may determine its horizontal
position in accordance with conventional techniques, the focus in Figure 5 is how the terminal
device may establish an indication of its altitude in accordance with embodiments of the
disclosure.
In step S2 the terminal device 420 uses its pressure sensor 428 to establish a measurement of
barometric pressure in the vicinity of the terminal device. This step may be performed in
accordance with conventional pressure measurement techniques. The measurement of
barometric pressure (or at least an indication of the measurement of barometric pressure) is
reported by the pressure sensor 428 to the controller unit 424 of the terminal device 420.
In step S3 of the processing represented in Figure 5, the base station establishes calibration
information to be used for establishing a height of the terminal device from the barometric
pressure measurement made in step S2. In this example implementation it is assumed the
calibration information is based on a measurement of barometric pressure made by the base
station 404. In particular, it is assumed here the calibration information comprises an estimate of
what the sea-level pressure P0 would be at the horizontal position of the base station having
regard to pressure measured at the altitude of the base station. In effect, the calibration
information is a normalized version of the pressure measured by the base station itself. The
base station is at a known fixed altitude and so pressure measurements at the base station can
be readily converted to corresponding pressure measurements at sea level in accordance with
conventional techniques (e.g. using a barometric formula such as those described above).
In step S4 the base station conveys an indication of the calibration information to the terminal
device.
There are various ways in which step S3 and step S4 may be performed. In this example it is
assumed the base station is configured to perform step S3 according to a predefined regular
schedule and to convey the indication of the calibration information to the terminal device (and
other terminal devices) in broadcast information (i.e. information that is receivable by a plurality
of terminal devices), for example in association with transmissions of system information.
Accordingly, and although not shown in Figure 5, with this approach the terminal device
receives an indication of calibration information from the base station on a regular cycle
regardless of whether or not the terminal device has decided a height estimate should be made.
However, in other examples the base station may be configured to provide calibration
information to the terminal device in a dedicated manner in response to a request received from
the terminal device. For example, the terminal device 420 may be configured to send a request
message to the base station 404 to ask the base station to performed steps S3 and S4. In
general, the transfer of the calibration information may be performed in accordance with any
known signaling techniques for exchanging data in wireless telecommunications systems.
In step S5 the terminal device uses the measurement of barometric pressure obtained in step
S2 and the calibration information received from the base station in step S4 to establish an
estimate of altitude / height relative to the reference altitude associated with the reference
barometric pressure comprising the calibration information. This step may be performed using
any of the well-established techniques for determining the height of a barometer from its
pressure measurements and a reference pressure measurement at a reference altitude, which
in this case is the indication of the pressure at sea level for the location of the base station. For
example, either of the Equations 1 and 2 could form the basis for the determination of height
made in step S5. In this regard, a value for temperature T may be assumed (e.g. corresponding
to an average temperature), or as described further below, a value of temperature T for use in a
barometric formula used in step S5 may be based on a measured value for temperature, for
example a measure of temperature made by the terminal device.
In this example implementation it is assumed the altitude of the terminal device is being
determined because it is needed by another element of the wireless telecommunications
system, for example a terminal device associated with an emergency responder seeking to
locate the terminal device 420. Thus, in step S6 the terminal device 420 conveys an indication
of the determine height information to the base station 404. The transfer of the indication of the
determined height from the terminal device 420 to the base station 404 may again be performed
in accordance with any known signaling techniques for exchanging data in wireless
telecommunications systems.
In step S7 the base station forwards the indication of the determined height as appropriate, for
example routing it on towards the terminal device of an emergency responder seeking to locate
the terminal device 420.
Thus, the processing described above with reference to Figure 5 shows one approach for
determining the height (altitude) of a terminal device in a wireless telecommunications system
based on a measurement of barometric pressure at the terminal device and a measurement of
barometric pressure at the base station. In accordance with this approach it is in effect assumed
the pressure at sea level at the horizontal location of the terminal device corresponds with the
pressure at sea level at the horizontal location of the base station.
It will be appreciated the approach described above may be modified in various ways. For
example, whereas in step S3 described above the calibration information established by the
base station comprises an indication of a reference barometric pressure normalized to sea
level, the calibration information could instead comprise an indication of the pressure measured
at the base station and an indication of the height of the base station. In effect, with this
approach the height of the base station (instead of sea level) is used as the reference altitude
for the reference barometric pressure. Accordingly, the terminal device in effect determines its
altitude relative to the height of the base station, rather than to sea level. The altitude of the
base station may then be added to the height determined by the terminal device to provide an
altitude for the terminal device relative to sea level if desired. This last step can be performed by
the base station, or could be performed by the terminal device if the terminal devices is aware of
the height of the base station (for example from a database stored at the terminal device or from
information broadcast by the base station). Furthermore, the calibration information for the
location of the base station may be determined from meteorological data supplied to the base
station rather than from a measurement of pressure at the base station itself.
Figure 6 is a ladder diagram schematically representing modes of operation of the base station
404 and the terminal device 420 represented in Figure 4 in accordance with some other
embodiments of the disclosure. The approach of Figure 6 is generally similar to, and will be
generally understood from, the approach of Figure 5. However, whereas in the approach of
Figure 5 it is the terminal device 420 that determines its height using its measurement of
barometric pressure and calibration information received from the base station, in the approach
of Figure 6 it is the base station that determines the height of the terminal devices using the
calibration information it has established and an indication of the terminal device's measurement
of barometric pressure received from the terminal device.
Thus steps T 1 and T2 of Figure 6 may be performed in the same manner as steps S 1 and S2 of
Figure 5. However, in step T3 Figure 6, the terminal device conveys an indication of the
barometric pressure measurement obtained from step T2 to the base station. This is in contrast
to the base station conveying an indication of the calibration information to the terminal device
in Step S4 of Figure 5. Again, the transfer of the indication of the barometric pressure
measurement from the terminal device 420 to the base station 404 may be performed in
accordance with any known signaling techniques for exchanging data in wireless
telecommunications systems.
Step T4 of the processing represented in Figure 6 is similar to, and will be understood from,
step S3 of Figure 5. However, in this example it is assumed the base station is configured to
perform step T4 in response to receiving the indication of the barometric pressure measurement
from the terminal device in step T3. The calibration information established in step T4 may
otherwise correspond with that established in step S3 described above.
Step T5 of the processing represented in Figure 6 is similar to and will be understood from the
processing represented in step S5 in Figure 5. However, in accordance with the approach of
Figure 6, the determination of the height based on the barometric pressure measurement from
the terminal device and the calibration information established by the base station is performed
by the base station, rather than by the terminal device. The processing may otherwise be the
same in both cases.
In this example implementation it is again assumed the altitude of the terminal device is being
determined because it is needed by another element of the wireless telecommunications
system, for example a terminal device associated with an emergency responder seeking to
locate the terminal device 420. Thus, in step T6 the base station forwards the indication of the
determined height as appropriate, for example routing it on towards the terminal device of an
emergency responder seeking to locate the terminal device 420. In some cases the base station
may also convey an indication of the determined height back to the terminal device, but this
may not be required.
Thus, the approach of Figure 6 is based on the same principles as the approach of Figure 5,
except it is the base station rather than the terminal device which has access to both the
calibration information and the measured barometric pressure to determine the height of the
terminal device.
As already noted, in the approaches of Figure 5 and 6, the calibration information corresponds
with a reference barometric pressure for the horizontal location of the base station and the
height determination in effect assumes the reference barometric pressure is also applicable for
the horizontal location of the terminal device. To reduce the impact of this effect, in some
implementations the terminal device may be configured to receive calibration information from a
plurality of surrounding base stations and to interpolate calibration information relevant for its
own horizontal location based on the reference barometric pressure measurements received
from the surrounding base stations and their corresponding locations. The locations of the base
stations may be conveyed to the terminal device in signaling or stored in a database at the
terminal device, or the terminal device may simply determine a distance to the respective base
stations based on the respective strength of the signaling received from the respective base
stations or based on the time taken for signaling to travel between the terminal device and the
respective base station (propagation delay). The terminal device may generate an average
reference barometric pressure based on a weighted average of the reference barometric
pressure is received from the different base stations, with the weighting been based on their
distances (i.e. with more weight given to nearby base stations). In effect this provides for the
interpolation of calibration information from multiple base stations. In this regard it would be
beneficial for each base station's reference pressure to correspond with a common reference
altitude (e.g. sea level) to reduce the complexity of computation required at the terminal device.
In another approach the calibration information (reference barometric pressure for a reference
altitude (e.g. sea level)) may be information relating to the horizontal location of the terminal
device itself.
For example, steps corresponding to steps S3 and T4 may be modified in accordance with
other embodiments of the disclosure to have the base station establish calibration information
that also takes account of the horizontal location of the terminal device. For example, the base
station may obtain meteorological data comprising a weather report for the region containing the
terminal device, and on determining the height estimate is being made by the terminal device
may be configured to establish a reference barometric pressure (e.g. assumed sea level
pressure) for the location of the terminal device from the meteorological data. The base station
may determine the horizontal location of the terminal device from existing mobility data in the
network, or in the alternative, the terminal device may be configured to report its horizontal
location, for example determined using a GPS receiver, to the base station in association with a
request for calibration information. Calibration information relevant for the location of the
terminal device that is established in this way may otherwise be used to determine the height of
the terminal device in the same manner as described. In principle, rather than have the base
station determine an indication of the terminal device's horizontal location to establish an
appropriate reference pressure for that location to convey as calibration information to the
terminal device, the base station may instead convey calibration information to the terminal
device comprising data representing a map of reference pressures for a region in which the
terminal device is located, and the terminal device may then determine an appropriate reference
pressure from the map of reference pressures based on its own knowledge of its own location
(for example determined from GPS).
It will be appreciated there will generally be a degree of temperature dependence in how a
given pressure measurement translates to a height measurement. For example, assuming
typical values near the Earth surface, a change in temperature of around 1K would change the
pressure at 100 m by around 0.035 mbar (equivalent to a height difference of around 35 cm).
Nonetheless, if desired account may also be taken of temperature. This can be achieved by
providing the terminal device with a temperature sensor and using measurements of the
temperature T at the terminal device in an appropriate barometric formula (e.g. as opposed to
using an assumed fixed value for temperature that might be considered appropriate for other
implementations). In this regard, the terminal device may be configured to use its measurement
of temperature T when determining its altitude in accordance with a step corresponding to step
S5 of Figure 5, for example using a barometric formula corresponding to that of Equation 2
above, but modified to replace T0 with T + Lh. Likewise, if the corresponding barometric formula
for an isothermal atmosphere is being used (Equation 1) , the value of T in this equation may
correspond with the measurement of temperature made by the terminal device (as opposed to a
fixed assumed value which might be adopted for some other implementations). In embodiments
of the disclosure in which the base station is responsible for determining the altitude of the
terminal device, the terminal device may be configured to convey an indication of its
temperature measurement to the base station in a step corresponding to T4 of Figure 6, and the
base station may then use the temperature information in a step corresponding to T5, in
accordance with the relevant barometric formula that has been adopted.
It will further be appreciated that while the above-described embodiments have focused on
implementations in which a base station establishes calibration information to be used in
conjunction with a pressure measurement from a terminal device to help establish the altitude /
height of the terminal device, in other examples other network entities may provide the
calibration information. For example, in some examples it may be a second terminal device,
instead of a base station, that establishes calibration information to be used to determine the
height of a first terminal device from a barometric pressure measurement associated with the
first terminal device. For example, in a situation where a second terminal device has already
established its own height (for example because it is manually entered by an operator of the
second terminal device based on some external reference or because the second terminal
device has established its own height with assistance from a base station in accordance with
the principles described above with reference to Figures 5 and 6), the second terminal device
may then be the network entities which provides calibration information to the first terminal
device, for example based on a pressure measurement made by the second terminal device. In
this regard, the nature of the calibration information provided by the second terminal device and
the manner in which it is used by the first terminal device may follow the same principles as
described above for examples in which the calibration information is established by a base
station. In some implementations, the second terminal device might not even establish its own
height in any absolute sense. For example, the second terminal device may simply transmit its
own pressure measurements to the first terminal device as calibration information. The first
terminal device may then determine its height relative to the height of the second terminal
device based on differences in its own pressure measurement as compared to the reference
pressure measurement received from the second terminal device. This will allow the first
terminal device to determine its height relative to the height of the second terminal device, and
this may, for example, be reported back to the second terminal device. Thus, an operator of the
second terminal device is provided with an indication of how far the first terminal device is
above or below the operator. In this regard, the reference height associated with the reference
pressure measurement may simply be the current height of the second terminal device. This
approach may thus provide an emergency responder with an indication of whether or not they
are currently on the same floor of a building as the first terminal device, or whether the first
terminal device is above or below them, and if so, by how far. Conversely, the first terminal
device may be configured to transmit its pressure measurements to the second terminal device,
so the second terminal device compares the measurement with its own measurements of
pressure to determine when they are the same, thereby identifying that the second terminal
device is at the same height (e.g. on the same floor of a building) as the first terminal device.
Thus there has been described methods and apparatus for determining an altitude for a
terminal device operating in a wireless telecommunications network comprising the terminal
device and another network entity (e.g. a base station or another terminal device). The terminal
device measures an indication of barometric pressure in its vicinity using a barometric sensor.
The other network entity establishes calibration information for terminal device's barometric
pressure measurement. The calibration information comprises a reference barometric pressure
for a reference altitude and may come from a barometric pressure measurement at the other
network entity or from meteorological data provided to the other network entity. The altitude of
the terminal device relative to the reference altitude may then be determined from the difference
between the barometric pressure measured by the terminal device and the reference barometric
pressure. The altitude may be determine by the terminal device after receiving the calibration
information from the other network entity and / or by the other network entity after receiving an
indication of the barometric pressure measured by terminal device.
Further particular and preferred aspects of the present invention are set out in the
accompanying independent and dependent claims. It will be appreciated that features of the
dependent claims may be combined with features of the independent claims in combinations
other than those explicitly set out in the claims.
Thus, the foregoing discussion discloses and describes merely exemplary embodiments of the
present invention. As will be understood by those skilled in the art, the present invention may be
embodied in other specific forms without departing from the spirit or essential characteristics
thereof. Accordingly, the disclosure of the present invention is intended to be illustrative, but not
limiting of the scope of the invention, as well as other claims. The disclosure, including any
readily discernible variants of the teachings herein, define, in part, the scope of the foregoing
claim terminology such that no inventive subject matter is dedicated to the public.
Respective features of the present disclosure are defined by the following numbered
paragraphs:
Paragraph 1. A method of determining an altitude of a terminal device operating in a wireless
telecommunications network comprising the terminal device and another network entity, the
method comprising: measuring, by the terminal device, an indication of barometric pressure in
the vicinity of the terminal device; establishing, at the other network entity, calibration
information for the indication of barometric pressure measured at the terminal device; and
determining the altitude of the terminal device from the indication of barometric pressure
measured by the terminal device and the calibration information established at the other
network entity.
Paragraph 2. The method of paragraph 1, further comprising the other network entity
conveying an indication of the calibration information to the terminal device, and wherein the
terminal device performs the step of determining the altitude of the terminal device from the
indication of barometric pressure measured by the terminal device and the calibration
information established at the other network entity.
Paragraph 3. The method of paragraph 2, further comprising the terminal device conveying an
indication of the determined altitude to the other network entity.
Paragraph 4. The method of paragraph 3, further comprising the other network entity
forwarding an indication of the determined altitude to another element of the wireless
telecommunications network.
Paragraph 5. The method of any of paragraphs 2 to 4, wherein the indication of the calibration
information is conveyed to the terminal device in broadcast signalling transmitted by the other
network entity.
Paragraph 6. The method of paragraph 5, wherein the indication of the calibration information
is conveyed to the terminal device in association with network information transmitted by the
other network entity.
Paragraph 7. The method of any of paragraphs 2 to 6, further comprising the terminal device
receiving an indication of further calibration information established by at least one further other
network entity, and wherein the altitude of the terminal device is determined by the terminal
device using the further calibration information received from the at least one further other
network entity.
Paragraph 8. The method of paragraph 7, wherein the step of determining the altitude of the
terminal device takes account of the relative distances between the terminal device and the
other network entity and between the terminal device and the at least one further other network
entity.
Paragraph 9. The method of claim 8, further comprising determining the relative distances
between the terminal device and the other network entity and further other network entity from
signal strengths and / or signal propagation delays associated with signalling between the
terminal device and the respective network entities.
Paragraph 10. The method of any of paragraphs 1 to 9, further comprising the terminal device
conveying an indication of barometric pressure measured by the terminal device to the other
network entity, and wherein the other network entity performs the step of determining the
altitude of the terminal device from the indication of barometric pressure measured by the
terminal device and the calibration information established at the other network entity.
Paragraph 11. The method of paragraph 10, further comprising the other network entity
conveying an indication of the determined altitude to the terminal device.
Paragraph 12. The method of paragraph 10 or 11, further comprising the other network entity
forwarding an indication of the determined altitude to another element of the wireless
telecommunications network.
Paragraph 13. The method of any of paragraphs 1 to 12, wherein the calibration information
comprises an indication of a reference barometric pressure for a reference altitude.
Paragraph 14. The method of paragraph 13, wherein the altitude of the terminal device is
determined relative to the reference altitude from a difference between the indication of the
barometric pressure measured by the terminal device and the indication of the reference
barometric pressure.
Paragraph 15. The method of paragraph 13 or 14, wherein the altitude of the terminal device
relative to the reference altitude is determined by comparing the difference between the
indication of the barometric pressure measured by the terminal device and the indication of the
reference barometric pressure with a model of variations in barometric pressure with altitude.
Paragraph 16. The method of any of paragraphs 13 to 15, wherein the indication of the
reference barometric pressure comprises an indication of barometric pressure in the vicinity of
the other network entity.
Paragraph 17. The method of paragraph 16, wherein the indication of barometric pressure in the
vicinity of the other network entity is an indication of barometric pressure measured by the other
network entity.
Paragraph 18. The method of paragraph 16 or 17, wherein reference altitude is an altitude of the
other network entity.
Paragraph 19. The method of any of paragraphs 13 to 18, further comprising the other network
entity obtaining meteorological data for a region containing the terminal device and an indication
of a horizontal position for the terminal device within the region, and wherein the indication of
the reference barometric pressure comprises an indication of barometric pressure in the vicinity
of the terminal device for the reference altitude which is established by the other network entity
from the meteorological data.
Paragraph 20. The method of any of paragraphs 1 to 19, further comprising the terminal device
establishing an indication of its horizontal position and conveying the indication of its horizontal
position to the other network entity.
Paragraph 2 1. The method of any of paragraphs 1 to 20, wherein the indication of the terminal
device's horizontal position is determined using a GPS receiver unit and / or a wireless local
area network transceiver unit and / or a Bluetooth transceiver unit.
Paragraph 22. The method of any of paragraphs 1 to 2 1, wherein the other network entity is a
other network entity of the wireless telecommunication network.
Paragraph 23. The method of any of paragraphs 1 to 2 1, wherein the other network entity is
anther terminal device operating in the wireless telecommunication network.
Paragraph 24. A wireless telecommunications network, comprising: a terminal device configured
to measure an indication of barometric pressure at the terminal device; and another network
entity configured to establish calibration information for the indication of barometric pressure
measured at the terminal device, wherein at least one of the terminal device and the other
network entity is configured to determine an indication of an altitude of the terminal device from
the indication of barometric pressure measured at the terminal device and the calibration
information established at the other network entity.
Paragraph 25. A method of operating a terminal device in a wireless telecommunications
network to determine an altitude for the terminal device; the method comprising: measuring an
indication of barometric pressure at the terminal device; receiving calibration information for the
indication of barometric pressure measured at the terminal device from another network entity;
and determining the altitude of the terminal device from the indication of barometric pressure
measured at the terminal device and the calibration information received from the other network
entity.
Paragraph 26. A terminal device comprising: a pressure sensor configured to measure an
indication of barometric pressure; a transceiver unit configured to receive calibration information
for the indication of barometric pressure measured by the terminal device from another network
entity; and a controller unit configured to determine an indication of an altitude of the terminal
device from the indication of barometric pressure measured by the terminal device and the
calibration information received from the other network entity.
Paragraph 27. Circuitry for a terminal device comprising a controller element and a transceiver
element configured to operate together to: obtain an indication of a measurement of barometric
pressure made by the terminal device; receive calibration information for the indication of the
measurement of barometric pressure made by the terminal device from another network entity;
and determine an indication of an altitude of the terminal device from the indication of a
measurement of barometric pressure made by the terminal device and the calibration
information received from the other network entity.
Paragraph 28. A method of operating a base station in a wireless telecommunications network
to determine an altitude for a terminal device; the method comprising: receiving from the
terminal device an indication of a measurement of barometric pressure made by the terminal
device; establishing calibration information for the indication of the measurement of barometric
pressure made by the terminal device; and determining an indication of an altitude of the
terminal device from the indication of the measurement of barometric pressure made by the
terminal device and the calibration information established by the base station.
Paragraph 29. A base station comprising: a transceiver unit configured to receive from a
terminal device an indication of a measurement of barometric pressure made by the terminal
device; a calibration information generation unit configured to establish calibration information
for the indication of the measurement of barometric pressure made by the terminal device; and
a controller unit configured to determine an indication of an altitude of the terminal device from
the indication of the measurement of barometric pressure made by the terminal device and the
calibration information established by the base station.
Paragraph 30. Circuitry for a base station comprising a controller element and a transceiver
element configured to operate together to: receive from the terminal device an indication of a
measurement of barometric pressure made by the terminal device; establish calibration
information for the indication of the measurement of barometric pressure made by the terminal
device; and determine an indication of an altitude of the terminal device from the indication of
the measurement of barometric pressure made by the terminal device and the calibration
information established by the base station.
REFERENCES
[1] FCC publication FCC-14-13, Wireless E91 1 Location Accuracy Requirements, PS
Docket No. 07-1 14, Adopted: February 20, 2014 Released: February 2 1, 2014 -
https://apps.fcc.gov/edocs_public/attachmatch/FCC-14-13A1 .pdf [1])
[2] Holma H. and Toskala A, "LTE for UMTS OFDMA and SC-FDMA based radio
access", John Wiley and Sons, 2009.
[3] BMP180 digital barometric pressure sensor from Bosch Sensortec - http://www.boschsensortec.
com/en_GB/homepage/products_3/environmental_sensors_1/bmp180_1/bmp180
[4] BMP280 barometric pressure sensor from Bosch Sensortec - http://www.boschsensortec.
com/en_GB/homepage/products_3/environmental_sensors_1/bmp280/bmp280
[5] BME280 integrated environmental sensor from Bosch Sensortec - http://www.boschsensortec.
com/en_GB/homepage/products_3/environmental_sensors_1/bme280/bme280_1

CLAIMS
What is claimed is:
1. A method of determining an altitude of a terminal device operating in a wireless
telecommunications network comprising the terminal device and another network entity, the
method comprising:
measuring, by the terminal device, an indication of barometric pressure in the vicinity of
the terminal device;
establishing, at the other network entity, calibration information for the indication of
barometric pressure measured at the terminal device; and
determining the altitude of the terminal device from the indication of barometric pressure
measured by the terminal device and the calibration information established at the other
network entity.
2. The method of claim 1, further comprising the other network entity conveying an
indication of the calibration information to the terminal device, and wherein the terminal device
performs the step of determining the altitude of the terminal device from the indication of
barometric pressure measured by the terminal device and the calibration information
established at the other network entity.
3. The method of claim 2, further comprising the terminal device conveying an indication of
the determined altitude to the other network entity.
4. The method of claim 3, further comprising the other network entity forwarding an
indication of the determined altitude to another element of the wireless telecommunications
network.
5. The method of claim 2, wherein the indication of the calibration information is conveyed
to the terminal device in broadcast signalling transmitted by the other network entity.
6. The method of claim 5, wherein the indication of the calibration information is conveyed
to the terminal device in association with network information transmitted by the other network
entity.
7. The method of claim 2, further comprising the terminal device receiving an indication of
further calibration information established by at least one further other network entity, and
wherein the altitude of the terminal device is determined by the terminal device using the further
calibration information received from the at least one further other network entity.
8. The method of claim 7, wherein the step of determining the altitude of the terminal
device takes account of the relative distances between the terminal device and the other
network entity and between the terminal device and the at least one further other network entity.
9. The method of claim 8, further comprising determining the relative distances between
the terminal device and the other network entity and further other network entity from signal
strengths and / or signal propagation delays associated with signalling between the terminal
device and the respective network entities.
10. The method of claim 1, further comprising the terminal device conveying an indication of
barometric pressure measured by the terminal device to the other network entity, and wherein
the other network entity performs the step of determining the altitude of the terminal device from
the indication of barometric pressure measured by the terminal device and the calibration
information established at the other network entity.
11. The method of claim 10, further comprising the other network entity conveying an
indication of the determined altitude to the terminal device.
1 . The method of claim 10, further comprising the other network entity forwarding an
indication of the determined altitude to another element of the wireless telecommunications
network.
13. The method of claim 1, wherein the calibration information comprises an indication of a
reference barometric pressure for a reference altitude.
14. The method of claim 13, wherein the altitude of the terminal device is determined relative
to the reference altitude from a difference between the indication of the barometric pressure
measured by the terminal device and the indication of the reference barometric pressure.
15. The method of claim 13, wherein the altitude of the terminal device relative to the
reference altitude is determined by comparing the difference between the indication of the
barometric pressure measured by the terminal device and the indication of the reference
barometric pressure with a model of variations in barometric pressure with altitude.
16. The method of claim 13, wherein the indication of the reference barometric pressure
comprises an indication of barometric pressure in the vicinity of the other network entity.
17. The method of claim 16, wherein the indication of barometric pressure in the vicinity of
the other network entity is an indication of barometric pressure measured by the other network
entity.
18. The method of claim 16, wherein reference altitude is an altitude of the other network
entity.
19. The method of claim 13, further comprising the other network entity obtaining
meteorological data for a region containing the terminal device and an indication of a horizontal
position for the terminal device within the region, and wherein the indication of the reference
barometric pressure comprises an indication of barometric pressure in the vicinity of the terminal
device for the reference altitude which is established by the other network entity from the
meteorological data.
20. The method of claim 1, further comprising the terminal device establishing an indication
of its horizontal position and conveying the indication of its horizontal position to the other
network entity.
2 1. The method of claim 1, wherein the indication of the terminal device's horizontal position
is determined using a GPS receiver unit and / or a wireless local area network transceiver unit
and / or a Bluetooth transceiver unit.
22. The method of claim 1, wherein the other network entity is a base station of the wireless
telecommunication network.
23. The method of claim 1, wherein the other network entity is anther terminal device
operating in the wireless telecommunication network.
24. A wireless telecommunications network, comprising:
a terminal device configured to measure an indication of barometric pressure at the
terminal device; and
another network entity configured to establish calibration information for the indication of
barometric pressure measured at the terminal device,
wherein at least one of the terminal device and the other network entity is configured to
determine an indication of an altitude of the terminal device from the indication of barometric
pressure measured at the terminal device and the calibration information established at the
other network entity.
25. A method of operating a terminal device in a wireless telecommunications network to
determine an altitude for the terminal device; the method comprising:
measuring an indication of barometric pressure at the terminal device;
receiving calibration information for the indication of barometric pressure measured at
the terminal device from another network entity; and
determining the altitude of the terminal device from the indication of barometric pressure
measured at the terminal device and the calibration information received from the other network
entity.
26. A terminal device comprising:
a pressure sensor configured to measure an indication of barometric pressure;
a transceiver unit configured to receive calibration information for the indication of
barometric pressure measured by the terminal device from another network entity; and
a controller unit configured to determine an indication of an altitude of the terminal
device from the indication of barometric pressure measured by the terminal device and the
calibration information received from the other network entity.
27. Circuitry for a terminal device comprising a controller element and a transceiver element
configured to operate together to:
obtain an indication of a measurement of barometric pressure made by the terminal
device;
receive calibration information for the indication of the measurement of barometric
pressure made by the terminal device from another network entity; and
determine an indication of an altitude of the terminal device from the indication of a
measurement of barometric pressure made by the terminal device and the calibration
information received from the other network entity.
28. A method of operating a base station in a wireless telecommunications network to
determine an altitude for a terminal device; the method comprising:
receiving from the terminal device an indication of a measurement of barometric
pressure made by the terminal device;
establishing calibration information for the indication of the measurement of barometric
pressure made by the terminal device; and
determining an indication of an altitude of the terminal device from the indication of the
measurement of barometric pressure made by the terminal device and the calibration
information established by the base station.
29. A base station comprising:
a transceiver unit configured to receive from a terminal device an indication of a
measurement of barometric pressure made by the terminal device;
a calibration information generation unit configured to establish calibration information
for the indication of the measurement of barometric pressure made by the terminal device; and
a controller unit configured to determine an indication of an altitude of the terminal
device from the indication of the measurement of barometric pressure made by the terminal
device and the calibration information established by the base station.
30. Circuitry for a base station comprising a controller element and a transceiver element
configured to operate together to:
receive from the terminal device an indication of a measurement of barometric pressure
made by the terminal device;
establish calibration information for the indication of the measurement of barometric
pressure made by the terminal device; and
determine an indication of an altitude of the terminal device from the indication of the
measurement of barometric pressure made by the terminal device and the calibration
information established by the base station.