RADIO INTERFACE COMMON RECONFIGURATION
FIELD OFTHE INVENTION
The present invention relates to a method of requesting a radio interface common
reconfiguration, a base station, a method of performing a radio interface common
reconfiguration, user equipment and computer program products.
BACKGROUND
Single carrier wireless telecommunications systems are known. In those known systems,
radio coverage is provided to user equipment, for example mobile telephones, by
geographical area. A base station is located in each geographical area to provide
the required radio coverage. User equipment in the area served by a base station
receives information and data from the base station and transmits information and
data to the base station. In a High-Speed Downlink Packet Access (HSDPA)
telecommunications network, data and information is sent between user equipment
and a base station in data packets on a radio frequency carrier.
Information and data transmitted by the base station to the user equipment occurs on
radio frequency carriers known as downlink carriers. Information and data transmitted
by user equipment to the base station occurs on radio frequency carriers known as
uplink carriers.
In known wireless telecommunications systems operating in a single carrier mode, user
equipment can move between geographical base station coverage areas. Service
provided to user equipment is overseen by a Radio Network Controller (RNC). The RNC
communicates with user equipment and base stations and determines which base
station each user equipment is primarily connected to. Furthermore, the RNC acts to
control and communicate with a base station and user equipment when user
equipment moves from the geographical area served by one base station to a
geographical area served by another base station.
It has been proposed to allow base stations and user equipment to each transmit
simultaneously on more than one carrier. Furthermore, it has been proposed to allow
user equipment and base stations to receive simultaneously on more than one carrier.
Each carrier, both uplink and downlink, is typically independently power controlled by a
base station. Provision of more than one downlink carrier, for example on four
frequency carriers, allows for a n increase in data throughput to the user equipment.
Networks having more than two carriers may be referred to as "Multi Cell High-Speed
Downlink Packet Access" (MC-HSDPA) networks. The term "multi-carrier"' network used
herein is envisaged to cover the case where two (e.g. Dual Cell HSDPAand Dual cell
HSUPA), three, four or more downlink (or uplink) carriers are provided for in a network.
The provision of multi-carrier functionality may have associated problems. Accordingly,
it is desired to improve the operation of a wireless telecommunications network having
multi-carrier functionality.
SUMMARY
According to a first aspect, there is provided a method of requesting a radio interface
common reconfiguration to be made by each of a group of user equipment from
within a plurality of user equipment being supported by a base station in a multi-carrier
wireless communications system, the method comprising the steps of: determining the
radio interface common reconfiguration to be made by each of the group of user
equipment; encoding the radio interface common reconfiguration in a payload field of
an high speed shared control channel (HS-SCCH) order; encoding, in the HS-SCCH
order, a n indication associating the HS-SCCH order with the group of user equipment;
and transmitting the HS-SCCH order to the plurality of user equipment being supported
by the base station.
The first aspect recognises that one problem with existing multi-carrier functionality is
that should it be necessary to reconfigure the radio interface between user equipment
and a base station to, for example, save energy, reduce interference or for other
reasons, this can only be done by sending a message to each of the user equipment in
turn, requesting that they reconfigure their radio interface. It will be appreciated that
sending such a message to each user equipment in turn takes time and consumes
resources. This may lead to reduced opportunities to take advantage of any benefits
that such a reconfiguration may offer.
Accordingly, a determination may be made of a required radio interface
reconfiguration that is common to a group of user equipment being supported by a
base station. The group of user equipment may be a subset of all the user equipment
being supported by the base station. The reconfiguration may be the same
reconfiguration to be performed by all the user equipment in that group. Details of the
reconfiguration may then be encoded in an HS-SCCH order in, for example, a payload
field. Accordingly, the payload field may provide a n indication of the radio interface
reconfiguration required to be implemented by each user equipment within the group.
It will be appreciated that any appropriate encoding technique may be utilised to
encode the reconfiguration to be performed by the group of user equipment. An
indication may also be encoded in the HS-SCCH order which associates that order with
a predetermined group of user equipment. It will be appreciated that this indication
helps to differentiate the HS-SCCH order intended for a group of user equipment from
existing HS-SCCH orders intended for individual user equipment. The indication may
also indicate which of the groups of user equipment the HS-SCCH order is intended for.
The HS-SCCH order may then be transmitted to the plurality of user equipment being
supported by the base station.
Hence, it can be seen that a single HS-SCCH order can be transmitted to a group of
user equipment. This avoids the need to transmit individual messages to each of those
user equipment. The HS-SCCH order may identify which group of user equipment the
message is intended for, thus enabling user equipment not within that group to
disregard the message. However, those user equipment within the group may then
perform the requested radio interface changes which will then be implemented in
common across all user equipment within that group. That is to say that every user
equipment within the group will implement the requested change. Hence, a single
message can be sent to a group of user equipment to cause that group of user
equipment to make a common reconfiguration of their radio interface which reduces
the amount of time taken to perform the reconfiguration and minimises the amount of
resources utilised to effect the reconfiguration.
In one embodiment, the group of user equipment are in a cell dedicated channel
(Cell_DCH) state and the radio interface common reconfiguration comprises at least
one of activating at least one carrier, deactivating at least one carrier, changing
primary carrier, changing of serving cell, change between normal transmission and
discontinuous transmission, and change between normal reception and discontinuous
reception. Accordingly, the user equipment may be operating in the CELL_DCH state
in which a high throughput is required and so rapid changes to the radio interface to
support that high throughput may also be required. For groups of user equipment in the
CELLJDCH state it may be possible to activate or deactivate carriers, change the
primary carrier, change the serving cell, switch to and from discontinuous transmission
or reception, or perform other reconfigurations of the radio interface. In this way, it can
be seen that it is possible to deactivate or activate aspects of a large group of user
equipment very rapidly. For example, a base station can deactivate a particular
secondary carrier for a group or all groups of user equipment for the purposes of
interference control or energy saving. In the case of energy saving, the base station
may, as a result of low traffic, wish to turn off one of its carriers and therefore deactivate
secondary carriers for a group or all groups of user equipment.
In one embodiment, the step of encoding the indication comprises: appending a
modified cyclic redundancy check field to the HS-SCCH order, the modified cyclic
redundancy check field being derived from at ieast one field of the HS-SCCH order and
an identifier common to the group of user equipment. Accordingly, a modified cyclic
redundancy check field may be appended to the HS-SCCH order. This modified cyclic
redundancy check field may be calculated using a n identifier which is common to all
user equipment within a group. In embodiments, such a common identifier may be a
secondary High-speed downlink shared channel Radio Network Transaction Identifier
(H-RNTI) which is pre-allocated by the base station to the user equipment. Such preallocation
may be performed by the base station for other purposes or may be
signalled to the user equipment for this specific purpose. It will be appreciated that the
specific signalling of such secondary H-RNTIs provides the base station with more
control in assigning those common identifiers. Accordingly, it can be seen that by
modifying the cyclic redundancy check field with the identifier common to the user
equipment within a particular group, only those user equipment within that group who
possess that identifier will be able to perform a valid cyclic redundancy check and
therefore implement the requested reconfiguration. Typically, each user equipment
may initially attempt to perform the cyclic redundancy check using its unique identifier
and, if that fails, may attempt to perform the cyclic redundancy check using its
common identifier. All user equipment belonging to other groups will assume that
either the message is not intended for that user equipment or will assume that the
message is corrupt. In either event, all other user equipment will not implement the
requested reconfiguration.
In one embodiment, the step of encoding the indication comprises: appending a
modified header field to the HS-SCCH order, the modified header field encoding a n
identifier common to the group of user equipment. Accordingly, the header field of the
HS-SCCH order may be modified to encode the identifier common to the group of user
equipment. In other words, the modified header may indicate that the order is a multi¬
cast order intended for a group of user equipment. The user equipment may then, in
turn, apply modified processing to such a multi-cast order to determine whether the
message is intended for that user equipment. Hence, when the user equipment
receives the HS-SCCH order with the modified header, only those user equipment
having a secondary H-RNTI indicated by the header will attempt to decode the
message. All other user equipment will disregard the message. It will be appreciated
that the header may encode the H-RNTI itself or may encode a n indicator which
indicates, typically in a fewer number of bits, the group identifier of the group the user
equipment belongs to/. It will be appreciated that both the base station and user
equipment will be operable to derive the group identifier from the secondary H-RNTI.
In one embodiment, the step of encoding the indication comprises: appending a
modified header field to the HS-SCCH order, the modified header field encoding a n
indicator that the HS-SCCH order is intended for a group of user equipment.
Accordingly, the modified header may indicate that the HS-SCCH order is a modified
order intended for a group of user equipment.
In one embodiment, the step of encoding the indication comprises: appending a
modified header field to the HS-SCCH order, the modified header field encoding a
group indicator representative of an identifier common to the group of user equipment.
In one embodiment, the method comprises the steps of: determining a quantity of user
equipment being supported by the base station requiring the radio interface common
reconfiguration and encoding and transmitting a plurality of the HS-SCCH orders, each
of the plurality of the HS-SCCH orders being receivable by a n associated group of user
equipment have a size less than a predetermined maximum. A problem with
transmitting HS-SCCH orders to a group of user equipment is that each of those user
equipment will respond with a n acknowledgement that the common reconfiguration
has occurred, and these acknowledgement messages may overwhelm the base
station. In order to reduce the number of such acknowledgements being transmitted
at any one time a number of HS-SCCH orders are transmitted to suitably sized groups.
Accordingly, the number of user equipment for which the reconfiguration is required to
be made is determined. If the number of user equipment to be reconfigured is greater
than a predetermined threshold, then a number of HS-SCCH orders may be encoded
and transmitted, each of which affecting a number of user equipment less than the
threshold. In this way, the number of acknowledgement messages received can be
restricted to less than a predetermined amount in order to reduce load on the network
and the base station.
In one embodiment, the step of transmitting comprises transmitting at least one of the
plurality of the HS-SCCH orders at a time which is different from at least another of the
plurality of the HS-SCCH orders. Hence, by transmitting the HS-SCCH orders at different
times, the acknowledgement messages will likewise be more distributed, thus reducing
the peak load on the network and the base station.
In one embodiment the step of transmitting comprises: at least one of transmitting the
HS-SCCH order with a power level set for that user equipment within the group having a
lowest signal reception level and transmitting the HS-SCCH order on a plurality of
carriers. Accordingly, by transmitting the HS-SCCH order with a power level set for the
user equipment having the greatest degree of signal attenuation, it can be ensured
that the HS-SCCH order is received by that user equipment and by all other user
equipment within the group. Likewise, by transmitting the HS-SCCH order on each of
the carriers, the likelihood that the order is received by each user equipment is
increased. Also, in embodiments, the order transmitted on the different carriers may be
soft combined by the user equipment.
In one embodiment, the method comprises the step of: monitoring for
acknowledgement messages from each of the group of user equipment; and
at least one of retransmitting the HS-SCCH order and transmitting at least one HS-SCCH
order, each HS-SCCH order being encoded for one of the group of user equipment
which failed to transmit an acknowledgement message. Accordingly, the base station
may monitor for acknowledgement messages received from each user equipment
indicating that the requested reconfiguration has been received. After a
predetermined period, the base station may then determine whether to re-transmit the
HS-SCCH order to the group of user equipment or transmit individual messages to those
user equipment which have failed to acknowledge the previous HS-SCCH order.
According to a second aspect, there is provided a base station operable to request a
radio interface common reconfiguration to be made by each of a group of user
equipment from within a plurality of user equipment being supported by the base
station, the base station comprising: determination logic operable to determine the
radio interface common reconfiguration to be made by each of the group of user
equipment; encoding logic operable to encode the radio interface common
reconfiguration in a payload field of an HS-SCCH order and to encode, in the HS-SCCH
order, an indication associating the HS-SCCH order with the group of user equipment;
and transmission logic operable to transmit the HS-SCCH order to the plurality of user
equipment being supported by the base station.
In one embodiment, the group of user equipment are in a cell dedicated channel
(CelLDCH) state and the radio interface common reconfiguration comprises at least
one of activating at least one carrier, deactivating at least one carrier, changing
primary carrier, changing of serving cell, change between normal transmission and
discontinuous transmission, and change between normal reception and discontinuous
reception.
In one embodiment, the encoding logic is operable to append a modified cyclic
redundancy check field to the HS-SCCH order, the modified cyclic redundancy check
field being derived from at least one field of the HS-SCCH order and an identifier
common to the group of user equipment.
In one embodiment, the encoding logic is operable to append a modified header field
to the HS-SCCH order, the modified header field encoding an identifier common to the
group of user equipment.
In one embodiment, the encoding logic is operable to append a modified header field
to the HS-SCCH order, the modified header field encoding an indicator that the HSSCCH
order is intended for a group of user equipment.
In one embodiment, the encoding logic is operable to append a modified header field
to the HS-SCCH order, the modified header field encoding a group indicator
representative of an identifier common to the group of user equipment.
In one embodiment, the determining logic is operable to determine a quantity of user
equipment being supported by the base station requiring the radio interface common
reconfiguration and the encoding logic and transmission logic are operable to encode
and transmit a plurality of the HS-SCCH orders, each of the plurality of the HS-SCCH
orders being receivable by an associated group of user equipment have a size less
than a predetermined maximum.
In one embodiment, the transmission logic is operable to perform at least one of
transmitting the HS-SCCH order with a power level set for that user equipment within the
group having a lowest signal reception level and transmitting the HS-SCCH order on a
plurality of carriers.
In one embodiment, the transmission logic is operable to transmit at least one of the
plurality of the HS-SCCH orders at a time which is different from at least another of the
plurality of the HS-SCCH orders.
In one embodiment, base station comprises monitoring logic operable to monitor for
acknowledgement messages from each of the group of user equipment and the
encoding logic and transmission logic are operable to perform at least one of
retransmitting the HS-SCCH order and transmitting a plurality of HS-SCCH orders, each
of the plurality of HS-SCCH orders being encoded for one of the group of user
equipment which failed to transmit a n acknowledgement message.
According to a third aspect, there is provided a method of performing a radio interface
common reconfiguration in user equipment in response a request from a supporting a
base station, the method comprising the steps of: receiving a n HS-SCCH order from the
base station; decoding a n indication in the HS-SCCH order associating the HS-SCCH
order with a group of user equipment; determining whether the indication matches a
group with which the user equipment is associated; and if a match occurs, decoding
the radio interface common reconfiguration in the HS-SCCH order and performing the
radio interface common reconfiguration.
In one embodiment, the user equipment is in a cell dedicated channel (Cell_DCH)
state and the radio interface common reconfiguration comprises at least one of
activating at least one carrier, deactivating at least one carrier, changing primary
carrier, changing of serving cell, change between normal transmission and
discontinuous transmission, and change between normal reception and discontinuous
reception.
In one embodiment, the step of decoding and determining comprises extracting a
cyclic redundancy check field from the HS-SCCH order and performing a cyclic
redundancy check using a n identifier common to the group of user equipment.
Accordingly, if the normal cyclic redundancy check on the received HS-SCCH order
performed by the user equipment using its unique H- NTI fails, the user equipment may
then perform the cyclic redundancy check using the common identifier. Should the
cyclic redundancy check using the common identifier then prove positive, the user
equipment may then implement the requested reconfiguration.
In one embodiment, the step of decoding and determining comprises identifying the
indication in a header field of the HS-SCCH order indicating a group of user equipment
with which the HS-SCCH order is associated. Hence, the determination that the HSSCCH
order is associated with a group of user equipment may be determined directly
from the header field.
In one embodiment, the step of decoding and determining comprises identifying a n
indicator in a header field of the HS-SCCH order indicating that the HS-SCCH order is
associated with a group of user equipment, extracting a cyclic redundancy check field
from the HS-SCCH order and performing a cyclic redundancy check using a n identifier
common to the group of user equipment. Accordingly, should the user equipment
determine from the header field that the HS-SCCH order is intended for a group of user
equipment, then the user equipment may initially perform the cyclic redundancy check
using the common identifier, thereby obviating the need to perform a first cyclic
redundancy check using its unique H-RNTI.
In one embodiment, the method comprises the step of: sending a n acknowledgement
to the base station at a time offset dependent upon at least one of a random offset, a
fixed offset and a n offset derived from the unique identifier. In this way the
acknowledgement messages from user equipment may be distributed with time to
thereby prevent overload on the base station.
According to a fourth aspect, there is provided user equipment operable to perform a
radio interface common reconfiguration in response a request from a supporting a
base station, the user equipment comprising: reception Iogic operable to receive a n
HS-SCCH order from the base station; decoding Iogic operable to decode a n
indication in the HS-SCCH order associating the HS-SCCH order with a group of user
equipment; determining Iogic operable to determine whether the indication matches a
group with which the user equipment is associated; and reconfiguration Iogic operable,
in response to an indication from the determining Iogic that a match occurs, to
decode the radio interface common reconfiguration in the HS-SCCH order and to
perform the radio interface common reconfiguration.
In one embodiment, the user equipment is in a cell dedicated channel (CelLDCH)
state and the radio interface common reconfiguration comprises at least one of
activating at least one carrier, deactivating at least one carrier, changing primary
carrier, changing of serving cell, change between normal transmission and
discontinuous transmission, and change between normal reception and discontinuous
reception.
In one embodiment, decoding Iogic and determining Iogic is operable to extract a
cyclic redundancy check field from the HS-SCCH order and to perform a cyclic
redundancy check using a n identifier common to the group of user equipment.
In one embodiment decoding logic and determining logic is operable identify the
indication in a header field of the HS-SCCH order indicating a group of user equipment
with which the HS-SCCH order is associated.
In one embodiment decoding logic and determining logic is operable to identify a n
indicator in a header field of the HS-SCCH order indicating that the HS-SCCH order is
associated with a group of user equipment to extract a cyclic redundancy check field
from the HS-SCCH order and to perform a cyclic redundancy check using a n identifier
common to the group of user equipment.
In one embodiment the user equipment comprises transmission logic operable to send
a n acknowledgement to the base station at a time offset dependent upon at least one
of a random offset a fixed offset and a n offset derived from the unique identifier.
According to a fifth aspect there is provided a computer program product operable,
when executed on a computer, to perform the method steps of the first aspect.
According to a sixth aspect there is provided a computer program product operable,
when executed on a computer, to perform the method steps of the third aspect.
Further particular and preferred aspects are set out in the accompanying independent
and dependent claims. Features of the dependent claims may be combined with
features of the independent claims a s appropriate, and in combinations other than
those explicitly set out in the claims.
BRIEF DESCRIPTION OFTHE DRAWINGS
Embodiments of the present invention will now be described further, with reference to
the accompanying drawings, in which:
Figure 1 illustrates a wireless telecommunications system 10 according to one
embodiment
Figure 2 illustrates the general operation of user equipment when receiving a n HS-SCCH
order;
Figure 3 illustrates cyclic redundancy checking of a n HS-SCCH order; and
Figure 4 illustrates transmission of HS-SCCH orders and HS-DPCCH acknowledgements
between a base station and user equipment.
Figure 1 illustrates a wireless telecommunications system 10 according to one
embodiment. User equipment 50 roam through the wireless telecommunications
system. Base stations 20 are provided which support areas of radio coverage 30. A
number of such base stations 20 are provided and are distributed geographically in
order to provide a wide area of coverage to user equipment 50. When user equipment
is within an area served by a base station 30, communications may be established
between the user equipment and the base station over associated radio links. Each
base station typically supports a number of sectors within the geographical area of
service 30.
Typically a different antenna within a base station supports each associated sector.
Accordingly, each base station 20 has multiple antennas and signals sent through the
different antennas are electronically weighted to provide a sectorised approach. Of
course, it will be appreciated that Figure 1 illustrates a small subset of the total number
of user equipment and base stations that may be present in a typical communications
system.
The radio access network of the wireless communications system is managed by a
radio network controller (RNC) 40. The radio network controller 40 controls operation of
the wireless communications system by communicating with a plurality of base stations
over a backhaul communications link 60. The network controller also communicates
with user equipment 50 via each base station.
A radio network controller 40 maintains a neighbour list which includes information
about geographical relationships between sectors supported by base stations 20. In
addition, the radio network controller 40 maintains location information which provides
information on the location of user equipment 50 within the wireless communication
system 10. T e radio network controller is operable to route traffic via circuit switched
and packet switched networks. Hence, a mobile switching centre is provided with
which the radio network controller may communicate. The mobile switching centre
can communicate with a circuit switched network such as a public switched telephone
network (PSTN) 70. Similarly, a network controller can communicate with service
general package radio service support nodes (SGSNs) and a gateway general packet
support node (GGSN). The GGSN can communicate with a packet switched core such
a s for example, the Internet.
User equipment 50 typically transmits information and data to a base station 20 so that
it can be re-routed within a wireless telecommunications network. User equipment
may, for example, need to transmit data to the base station in order to relay text
messages, voice information when a user is using the equipment to make a telephone
call, or other data. The base station 20, in combination with parameters set by the
radio network controller 40, allocates resources to user equipment in a manner that
aims to optimise operation of the wireless telecommunications network 10.
In Universal Mobile Telecommunications System (UMTS), a Multi-Cell High Speed
Downlink Packet Access (MC-HSDPA) arrangement is provided. In MC-HSDPA a sector
is defined as the geographical coverage area of a base station or Node B. A sector
can consist of several cells, where each cell aims to cover the same geographical
coverage as the sector and uses a separate frequency carrier for its transmission. The
frequency carrier can be within the same frequency band or distributed over two
frequency bands. MC-HSDPA is a n extension to Dual Cell High Speed Downlink Packet
Access (DC-HSDPA). In MC-HSDPA user equipment can receive up to four
simultaneous downlink transmissions from four different cells. Hence, MC-HSDPAcan
potentially double and quadruple the downlink throughput of DC-HSDPAand (Single
Cell) HSDPArespectively. MC-HSDPAis also sometimes referred to as4C-HSDPA (four
Cell HSDPA) or 3C-HSDPAwhen the user equipment receives simultaneous transmissions
from four or three cells respectively.
In a multi-carrier system, each carrier will have independent downlink radio links from a
base station to user equipment. Those downlink radio links are managed
independently since each carrier will likely have different radio propagation paths to
user equipment. For HSDPAsystems capable of operating in multi-carrier mode, more
than two downlink carriers may be provided. It will be appreciated that in a multicarrier
network, the number of downlink carriers may not match the number of uplink
carriers. Furthermore, the number of downlink carriers provided may not be exactly
double the number of uplink carriers provided. In HSDPAmulti-carrier mode, each
sector served by a base station can have several carrier frequencies or "carriers"
associated therewith. A carrier or cell supported by a carrier covers the same
geographical region as a sector. Each cell is served by a different carrier frequency. It
will therefore be understood that in a single carrier system, a cell is equivalent to a
sector since a sector has only one cell or carrier frequency. Nonetheless, in a multicarrier
network each sector may comprise several cells each cell being served
simultaneously by a different carrier frequency.
User equipment can be in Idle mode or in Radio Resource Control (RRC) Connected
Mode. CelLDCH state is one of the states within RRC Connected Mode where user
equipment can transmit and receive high data throughput. The MC-HSDPAfeature
operates in CelLDCH state, where in this state user equipment and Node B maintain
physical layer synchronisations in the uplink and downlink. An HS-DSCH Radio Network
Transaction Identifier (H-RNTI) is a unique identifier for user equipment operating in
HSDPAand it is unique to each user equipment in CelLDCH state.
In addition, a secondary H-RNTI is allocated that is common to all o r a group of user
equipment being supported by the base station. A secondary H-RNTI used in
Enhanced Cell_FACH and CelLPCH states for sending common control signals via HSDSCH
may be utilised for this purpose, this set of secondary H-RNTIs being broadcast in
the System Information Broadcast (SIB) 5 and 5bis. Alternatively, a set of secondary HRNTIs
may be specifically allocated by the base station for this purpose. Specifically
allocating secondary H-RNTIs provides the base station with more control to limit the size
of the groups to reduce the number of concurrent acknowledgement messages being
generated by user equipment as will be described in more detail below.
In MC-HSDPA, the primary carrier is the cell that carries essential control channels and it
cannot be deactivated. There is only one primary carrier and the other cells are called
secondary carriers (e.g. Secondary Carrier 1, Secondary Carrier 2 and Secondary
Carrier 3). The user equipment will declare radio link failure if the primary carrier radio
link fails, even if the secondary carriers are working perfectly (e.g. if they are lightly
loaded or if they have a better radio channel). The secondary carriers provide natural
radio link redundancies but these redundancies cannot be utilised.
Control of the carriers can be effected using a n HS-SCCH (High Speed Shared Control
Channel) order. The HS-SCCH order is layer signalling from the supporting base station
to user equipment that allows fast commands/orders to be made. Apart from
deactivation/activation of secondary carriers, HS-SCCH orders can also be used to turn
on discontinuous transmission and reception.
Embodiments provide a technique enable fast reconfiguration of a large number of
user equipment to occur by utilising a modified HS-SCCH order. For example, there are
scenarios where the base station needs to deactivate or activate a large group of use
equipment in the cell. For example, it is beneficial if the base station can deactivate a
particular secondary carrier for a group o r all the user equipment for the purpose of
interference control or energy saving. In energy saving, the base station due to low
traffic conditions may wish to turn off one of its carriers and therefore deactivate
secondary carriers for all user equipment in the cell as will be described in more detail
below.
Figure 2 illustrates the general operation of user equipment when receiving a n HS-SCCH
order. In the example shown in Figure 2, the HS-SCCH order contains information
required to decode a corresponding High Speed Downlink Shared Channel (HS-DSCH)
or contains an order for the user equipment. When the HS-SCCH order is sent it is sent
two slots in advance, as shown in Figure 2, where the first slot contains the information
so that the user equipment can start decoding the HS-DSCH two slots later. This
therefore gives one slot (slot 2) for the user equipment to reconfigure itself.
As shown in Figure 2, the HS-SCCH order 105 comprises three main fields (other fields
have been omitted to improve clarity). These three main fields are a header field 100,
a payload field 110 and a cyclic redundancy check field 120. The cyclic redundancy
check is applied to HS-SCCH orders for error detection at the user equipment and is
typically masked with the H-RNTI unique to the user equipment in order to ensure that
only a cyclic redundancy check performed by that user equipment will pass.
As shown in Figure 2, at least three different modified forms of the HS-SCCH order 105A -
105C may be transmitted by the base station, these modified forms of the HS-SCCH
order may be considered to be broadcast or multicast orders since they are intended
to be received by more than one user equipment. A similar unicast form of these orders
may be utilised for those user equipment that fail to acknowledge the multicast order,
as will be described in more detail below.
In the first form of HS-SCCH order 105 a standard header field is utilised 100, together
with a six-bit order field 11OA which encodes the common reconfiguration to be made
by user equipment within a specified group. The cyclic redundancy check field 120A
includes a conventional cyclic redundancy check (16 bits) which is then masked with
the secondary H-RNTI (16 bits) common to all user equipment within the group as
illustrated in Figure 3.
In the second form of HS-SCCH order 105B, the header is a modified header 100B which
indicates that the HS-SCCH order is a modified HS-SCCH order intended for receipt by a
group of user equipment. The modified header field 100B also includes a n indication of
the group for which the order is intended. Typically, the group indicator will be an
encoded representation of the secondary H-RNTI which is derivable by both the base
station and the user equipment from that common H-RNTI. Again, the order is the same
as that mentioned above, whilst the cyclic redundancy check is a standard cyclic
redundancy check without any H-RNTI masking.
In the third form of HS-SCCH order 105C, a further modified header field lOOC is used
which indicates that the message is a multicast HS-SCCH order. The order field 11OA is
identical to the two messages described above, whilst the cyclic redundancy check
field 120A includes a cyclic redundancy check masked with the secondary H-RNTI.
Hence with the first form of HS-SCCH order 105A, the user equipment on receipt of the
message will perform standard processing on the HS-SCCH order using its unique H-RNTI
as illustrated in Figure 3. The masked CRC and H-RNTI are removed from the cyclic
redundancy check field 120A and it is (un)masked with the unique H-RNTI to extract the
cyclic redundancy check bits. The cyclic redundancy check bits are then decoded for
error detection. An error will occur if the HS-SCCH is not intended for the user
equipment since a different unique H-RNTI, intended for another user equipment (i.e.
the target user equipment), is used to mask the cyclic redundancy check at the base
station. It is also possible that the HS-SCCH fails the cyclic redundancy check decoding
even if the correct H-RNTI is used due to genuine errors in the HS-SCCH order. The user
will discard any HS-SCCH orders that fail the cyclic redundancy check decoding since
they contain errors. However, if the cyclic redundancy check fails, rather than simply
stopping processing there, the user equipment will then re-perform the cyclic
redundancy check using the secondary H-RNTI. If the cyclic redundancy check passes
then the user equipment will decode the order field 11OA using modified decoding for
multicast HS-SCCH orders. It will be appreciated that any appropriate encoding
technique may be utilised to encode the required information for reconfiguration of the
radio interface mentioned above.
However, it will be appreciated that a problem with the decoding of the first form of HSSCCH
order 105A is that the cyclic redundancy check needs to be performed twice.
Accordingly, in the second form of HS-SCCH order 105B, the configuration the header
field 100B indicates that the message is a multicast HS-SCCH order and provides a n
indication of the group that the order is intended for. Assuming that the indication
matches the group that the user equipment belongs to, then the user equipment will
perform cyclic redundancy checking without using its unique H-RNTI. Assuming the
cyclic redundancy check passes, then the user equipment will decode the order field
and implement the requested reconfiguration.
Likewise, with the third form of HS-SCCH order 05C, the user equipment is able to
derive from the modified header field lOOC that the message is a multicast HS-SCCH
order and will directly perform its cyclic redundancy check using its secondary H-RNTI.
This avoids the need to perform the cyclic redundancy check first using the unique HRNTI
and speeds the process. Assuming the cyclic redundancy check passes, then the
user equipment will decode the order field and perform the requested reconfiguration.
The base station will attempt to transmit the HS-SCCH orders 05A - 105C with a
sufficiently high power that it will reach all user equipment within the group. The HSSCCC
order can be transmitted with a maximum permissible power o r with a power
that would reach the user equipment with the poorest radio conditions (i.e. reach the
user equipment which is furthest away or which has the greatest level of signal
attenuation). The reliability of the HS-SCCH orders 105A - 105C can be further improved
by transmitted over all configured carriers. The received HS-SCCH orders from the
different carriers can then be soft combined at the base band level in the user
equipment. Hence, those user equipment with more than one active carrier will gain
extra reliability by receiving the same HS-SCCH order on more than one carrier.
When in the CELL_DCH state, a n HS-SCCH order is acknowledged by the user
equipment using the High Speed Dedicated Physical Control Channel (HS-DPCCH)
feedback channel. Accordingly, a n HS-SCCH order sent to a large group of user
equipment may trigger a large number of simultaneous transmissions of
acknowledgements over the HS-DPCCH). This may cause overload or interference at
the base station. Therefore, to reduce the number of acknowledgements received at
the base station at any one time, the HS-SCCH orders are broadcast to different groups
of user equipment at different times so that the feedback from each group arrives at
the base station at different times. The size of each group is selected so that the base
station can handle the possible simultaneous acknowledgements from these user
equipment and this size is controlled by controlling the allocation of secondary H-RNTIs.
Consider a n example of a 4C-HSDPA sector that has 40 user equipment with all four
carriers active. The carriers are named a s CI, C2, C3 and C4. CI is the primary carrier
and therefore cannot be deactivated. There are four secondary H-RNTIs allocated to
restrict the size of each group to no more than ten user equipment. The user
equipment dedicated and secondary H-RNTIs are allocated a s follows:
UE H-R TI
Dedicated Secondary
I to 10 1001 to 1010 10000
I I to 20 2001 to 2010 20000
2 1 to 30 3001 to 3010 30000
3 1 to 40 4001 to 4010 40000
Assume now that carriers C and C4 are overloaded. The base station decides to
deactivate carrier C2 for half of the user equipment and to deactivate carrier C4 for
the remaining half of user equipment, as follows:
UE Carrier to Deactivate
1 to 10 C2
to 20 C2
2 1 to 30 C4
3 1 to 40 C4
The base station therefore sends four separate HS-SCCH multicast orders with the
following configuration:
To avoid receiving a large number of simultaneous HS-DPCCH acknowledgement
messages, the base station sends HS-SCCH order 1 and HS-SCCH order 3 together and
then, after five timed intervals, sends HS-SCCH order 2 and HS-SCCH order 4 together.
This is illustrated in more detail in Figure 4.
In order to further reduce the number of simultaneous HS-DPCCH acknowledgement
transmissions from the user equipment each user equipment in the group may send its
HS-DPCCH acknowledgement at different times. Accordingly, each user equipment
may send its HS-DPCCH acknowledgement based on a random amount, a staggered
amount, a predetermined offset amount, or based on the user equipment's identifier.
In one embodiment, the offset is determined based on the dedicated H-RNTI a s follows:
HS-DPCCH_TTI = Dedicated H-RNTI MOD K
where HS-DPCCH_TTI is the amount of delay in transmission time intervals before sending
the HS-DPCCH acknowledgement; and K is a number provided by the base station (the
larger this number is the longer it will take for all acknowledgements to reach the base
station and therefore this number should balance the need to delay receiving all
acknowledgements and the number of simultaneous acknowledgements that the base
station can handle).
In the example mentioned above, there are two HS-SCCH multi-cast orders sent to 20
user equipment at each attempt. The simultaneous HS-DPCCH acknowledgements
from 20 user equipment may still not be tolerable at the base station. To further reduce
the number of simultaneous acknowledgements, the HS-DPCCH acknowledgements
are sent at different times using the above formula where K = 5. Using this arrangement,
the number of transmission time intervals to delay before sending the HS-DPCCH
acknowledgements for user equipment 1to 10 is shown below:
UE Dedicated H-RNTI Number of TTI to Delay
1 1001 1
2 1002 2
3 1003 3
4 1004 4
5 1005 0
6 1006 1
7 1007 2
8 1008 3
9 009 4
10 1010 0
In this example, user equipment 5 and 0 will send the HS-DPCCH acknowledgement
immediately, followed by user equipment 1 and 6 at one transmission time interval later.
Similar calculations can be performed for other groups of user equipment. In this way,
the base station receives only four HS-DPCCH acknowledgements at once, as
illustrated in more detail in Figure 4 .
Once the user equipment sends the HS-DPCCH acknowledgement, the user equipment
can execute the order and reconfigure its radio interface.
The base station will monitor for the acknowledgements from each user equipment. For
those user equipment that miss the HS-SCCH multicast order (which is determined by a
missing acknowledgement at the base station) the base station can resend a
dedicated HS-SCCH order to the specific user equipment (if the number of user
equipments failing to acknowledgement is small) or resend the HS-SCCH multicast order
(if the number of user equipment who fail to acknowledge is high).
In this example, user equipment 27 failed to decode the HS-SCCH order 3 and, hence,
did not receive the order. Since only one user equipment failed to receive the order,
the base station sends a dedicated HS-SCCH order to user equipment 27 to deactivate
carrier C4. In the second attempt, user equipment 27 receives the order and sends an
acknowledgement back via the HS-DPCCH feedback channel.
Accordingly, it can be seen that rather than having to transmit 40 individual HS-SCCH
orders to reconfigure the user equipment, only four multicast HS-SCCH orders need be
transmitted.
Hence, a technique is provided in which a base station may send a n HS-SCCH order to
a group of user equipment rather than sending individual orders to each user
equipment. This reduces the amount of orders that are needed to reconfigure a group
of user equipment. This is particularly useful when a base station needs to activate or
deactivate carriers for a group of user equipment for, for example, the purposes of load
balancing or energy saving.
A person of skill in the art would readily recognize that steps of various above-described
methods can be performed by programmed computers. Herein, some embodiments
are also intended to cover program storage devices, e.g., digital data storage media,
which are machine or computer readable and encode machine-executable or
computer-executable programs of instructions, wherein said instructions perform some
or all of the steps of said above-described methods. The program storage devices may
be, e.g., digital memories, magnetic storage media such as a magnetic disks and
magnetic tapes, hard drives, or optically readable digital data storage media. The
embodiments are also intended to cover computers programmed to perform said
steps of the above-described methods.
The functions of the various elements shown in the Figures, including any functional
blocks labelled as "processors" or "logic", may be provided through the use of
dedicated hardware as well as hardware capable of executing software in association
with appropriate software. When provided by a processor, the functions may be
provided by a single dedicated processor, by a single shared processor, or by a
plurality of individual processors, some of which may be shared. Moreover, explicit use
of the term "processor" or "controller" or "logic" should not be construed to refer
exclusively to hardware capable of executing software, and may implicitly include,
without limitation, digital signal processor (DSP) hardware, network processor,
application specific integrated circuit (ASIC), field programmable gate array (FPGA),
read only memory (ROM) for storing software, random access memory (RAM), and non
volatile storage. Other hardware, conventional and/or custom, may also be included.
Similarly, any switches shown in the Figures are conceptual only. Their function may be
carried out through the operation of program logic, through dedicated logic, through
the interaction of program control and dedicated logic, or even manually, the
particular technique being selectable by the implementer a s more specifically
understood from the context.
It should be appreciated by those skilled in the art that any block diagrams herein
represent conceptual views of illustrative circuitry embodying the principles of the
invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state
transition diagrams, pseudo code, and the like represent various processes which may
be substantially represented in computer readable medium and so executed by a
computer or processor, whether or not such computer or processor is explicitly shown.
The description and drawings merely illustrate the principles of the invention. It will thus
be appreciated that those skilled in the art will be able to devise various arrangements
that, although not explicitly described or shown herein, embody the principles of the
invention and are included within its spirit and scope. Furthermore, all examples recited
herein are principally intended expressly to be only for pedagogical purposes to aid the
reader in understanding the principles of the invention and the concepts contributed
by the inven†or(s) to furthering the art, and are to be construed as being without
limitation to such specifically recited examples and conditions. Moreover, all statements
herein reciting principles, aspects, and embodiments of the invention, as well as
specific examples thereof, are intended to encompass equivalents thereof.
CLAIMS
1. A method of requesting a radio interface common reconfiguration to be made
by each of a group of user equipment from within a plurality of user equipment being
supported by a base station in a multi-carrier wireless communications system, the
method comprising the steps of:
determining said radio interface common reconfiguration to be made by each
of said group of user equipment;
encoding said radio interface common reconfiguration in a payload field of an
high speed shared control channel (HS-SCCH) order;
encoding, in said HS-SCCH order, an indication associating said HS-SCCH order
with said group of user equipment; and
transmitting said HS-SCCH order to said plurality of user equipment being
supported by said base station.
2. The method of claim 1, wherein said group of user equipment are in a cell
dedicated channel (CelLDCH) state and said radio interface common reconfiguration
comprises at least one of activating at least one carrier, deactivating at least one
carrier, changing primary carrier, changing of serving cell, change between normal
transmission and discontinuous transmission, and change between normal reception
and discontinuous reception.
3. The method of claim 1 or 2, wherein said step of encoding said indication
comprises:
appending a modified cyclic redundancy check field to said HS-SCCH order,
said modified cyclic redundancy check field being derived from at least one field of
said HS-SCCH order and an identifier common to said group of user equipment.
4. The method of any preceding claim, wherein said step of encoding said
indication comprises:
appending a modified header field to said HS-SCCH order, said modified
header field encoding an identifier common to said group of user equipment.
5. The method of any preceding claim, wherein said step of encoding said
indication comprises:
appending a modified header field to said HS-SCCH order, said modified
header field encoding an indicator that said HS-SCCH order is intended for a group of
user equipment.
6. The method of any preceding claim, wherein said step of encoding said
indication comprises:
appending a modified header field to said HS-SCCH order, said modified
header field encoding a group indicator representative of a n identifier common to said
group of user equipment.
7. The method of any preceding claim, comprising the steps of:
determining a quantity of user equipment being supported by said base station
requiring said radio interface common reconfiguration and encoding and transmitting
a plurality of said HS-SCCH orders, each of said plurality of said HS-SCCH orders being
receivable by a n associated group of user equipment have a size less than a
predetermined maximum.
8. The method of any preceding claim, wherein said step of transmitting
comprises:
at least one of transmitting said HS-SCCH order with a power level set for that
user equipment within said group having a lowest signal reception level and
transmitting said HS-SCCH order on a plurality of carriers.
9 . The method of any preceding claim, comprising the step of:
monitoring for acknowledgement messages from each of said group of user
equipment; and
at least one of retransmitting said HS-SCCH order and transmitting a plurality of
HS-SCCH orders, each of said plurality of HS-SCCH orders being encoded for one of said
group of user equipment which failed to transmit a n acknowledgement message.
10. A base station operable to request a radio interface common reconfiguration
to be made by each of a group of user equipment from within a plurality of user
equipment being supported by said base station, the base station comprising:
determination logic operable to determine said radio interface common
reconfiguration to be made by each of said group of user equipment;
encoding logic operable to encode said radio interface common
reconfiguration in a payload field of a n HS-SCCH order and to encode, in said HS-SCCH
order, a n indication associating said HS-SCCH order with said group of user equipment;
and
transmission logic operable to transmit said HS-SCCH order to said plurality of
user equipment being supported by said base station.
1 . A method of performing a radio interface common reconfiguration in user
equipment in response a request from a supporting a base station, the method
comprising the steps of:
receiving an HS-SCCH order from said base station;
decoding an indication in said HS-SCCH order associating said HS-SCCH order
with a group of user equipment;
determining whether said indication matches a group with which said user
equipment is associated; and
if a match occurs, decoding said radio interface common reconfiguration in
said HS-SCCH order and performing said radio interface common reconfiguration.
12. The method of claim 11, wherein said step of decoding and determining
comprises extracting a cyclic redundancy check field from said HS-SCCH order and
performing a cyclic redundancy check using an identifier common to said group of
user equipment.
13. The method of claim 11or 2, wherein said step of decoding and determining
comprises identifying said indication in a header field of said HS-SCCH order indicating
a group of user equipment with which said HS-SCCH order is associated.
14. The method of any one of claims 1 to 13, wherein said step of decoding and
determining comprises identifying an indicator in a header field of said HS-SCCH order
indicating that said HS-SCCH order is associated with a group of user equipment,
extracting a cyclic redundancy check field from said HS-SCCH order and performing a
cyclic redundancy check using an identifier common to said group of user equipment.
15. User equipment operable to perform a radio interface common reconfiguration
in response a request from a supporting a base station, the user equipment comprising:
reception logic operable to receive a n HS-SCCH order from said base station;
decoding logic operable to decode an indication in said HS-SCCH order
associating said HS-SCCH order with a group of user equipment;
determining logic operable to determine whether said indication matches a
group with which said user equipment is associated; and
reconfiguration logic operable, in response to an indication from said
determining logic that a match occurs, to decode said radio interface common
reconfiguration in said HS-SCCH order and to perform said radio interface common
reconfiguration.