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Title of the Invention
COMMUNICATION SYSTEMS
Field of the Invention
Currently there exists significant interest in the use of multihop techniques in packet
based radio and other communication systems, where it is purported that such
techniques will enable both extension in coverage range and increase in system
capacity (throughput).
Background of the Invention
In a multi-hop communication system, communication signals are sent in a
communication direction along a communication path from a source apparatus to a
destination apparatus via one or more intermediate apparatuses. Figure 1 illustrates a
single-cell two-hop wireless communication system comprising a base station BS
(known in the context of 3G communication systems as "node-B" NB), a relay node RN
(also known as a relay station RS), and an item of user equipment UE (also known as
a mobile station MS or subscriber station SS; below, the abbreviation MS or MS/SS is
used to denote either of these types of UE). In the case where signals are being
transmitted on the downlink (DL) from a base station to a destination user equipment
(UE) via the relay node (RN), the base station comprises the source station (S) and the
user equipment comprises the destination station (D). In the case where
communication signals are being transmitted on the uplink (UL) from the user
equipment (UE), via the relay node, to the base station, the user equipment comprises

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the source station and the base station comprises the destination station. The latter
form of communication includes signals transmitted by the user equipment to identify
itself to the base station (and hence to the network) as part of a network entry
procedure. This is of particular relevance to the present invention as will be explained
below.
The relay node is an example of intermediate apparatus and comprises: a receiver,
operable to receive data from the source apparatus; and a transmitter, operable to
transmit this data, or a derivative thereof, to the destination apparatus.
Simple analogue repeaters or digital repeaters have been used as relays to improve or
provide coverage in dead spots. They can either operate in a different transmission
frequency band from the source station to prevent interference between the source
transmission and the repeater transmission, or they can operate at a time when there is
no transmission from the source station.
Figure 2 illustrates a number of applications for relay stations. For fixed infrastructure,
the coverage provided by a relay station may be "in-fill" to allow access to the
communication network for mobile stations which may otherwise be in the shadow of
other objects or otherwise unable to receive a signal of sufficient strength from the
base station despite being within the normal range of the base station. "Range
extension" is also shown, in which a relay station allows access when a mobile station
is outside the normal data transmission range of a base station. One example of in-fill

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shown at the top right of Figure 2 is positioning of a nomadic relay station to allow
penetration of coverage within a building that could be above, at, or below ground level.
Other applications are nomadic relay stations which are brought into effect for
temporary cover, providing access during events or emergencies/disasters. A final
application shown in the bottom right of Figure 2 provides access to a network using a
relay positioned on a vehicle.
Relays may also be used in conjunction with advanced transmission techniques to
enhance gain of the communications system as explained below.
It is known that the occurrence of propagation loss, or "pathloss", due to the scattering
or absorption of a radio communication as it travels through space, causes the strength
of a signal to diminish. Factors which influence the pathloss between a transmitter and
a receiver include: transmitter antenna height, receiver antenna height, carrier
frequency, clutter type (urban, sub-urban, rural), details of morphology such as height,
density, separation, terrain type (hilly, flat). The pathloss L (dB) between a transmitter
and a receiver can be modelled by:
L = b + 10n logd (A)
Where d (metres) is the transmitter-receiver separation, b(db) and n are the pathloss
parameters and the absolute pathloss is given by l = 10(L/10).

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The sum of the absolute path losses experienced over the indirect link SI + ID may be
less than the pathloss experienced over the direct link SD. In other words it is possible
for:
L(SI) + L(ID) < L(SD) (B)
Splitting a single transmission link into two (or more) shorter transmission segments
therefore exploits the non-linear relationship between pathloss verses distance. From
a simple theoretical analysis of the pathloss using equation (A), it can be appreciated
that a reduction in the overall pathloss (and therefore an improvement, or gain, in
signal strength and thus data throughput) can be achieved if a signal is sent from a
source apparatus to a destination apparatus via intermediate apparatus (one or more
relay nodes), rather than being sent directly from the source apparatus to the
destination apparatus. If implemented appropriately, multi-hop communication systems
can allow for a reduction in the transmit power of transmitters which facilitate wireless
transmissions, leading to a reduction in interference levels as well as decreasing
exposure to electromagnetic emissions. Alternatively, the reduction in overall pathloss
can be exploited to improve the received signal quality at the receiver without an
increase in the overall radiated transmission power required to convey the signal.
Multi-hop systems are suitable for use with multi-carrier transmission. In a multi-carrier
transmission system, such as FDM (frequency division multiplex), OFDM (orthogonal
frequency division multiplex) or DMT (discrete multi-tone), a single data stream is

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modulated onto N parallel sub-carriers, each sub-carrier signal having its own
frequency range. This allows the total bandwidth (i.e. the amount of data to be sent in
a given time interval) to be divided over a plurality of sub-carriers thereby increasing
the duration of each data symbol. Since each sub-carrier has a lower information rate,
multi-carrier systems benefit from enhanced immunity to channel induced distortion
compared with single carrier systems. This is made possible by ensuring that the
transmission rate and hence bandwidth of each subcarrier is less than the coherence
bandwidth of the channel. As a result, the channel distortion experienced on a signal
subcarrier is frequency independent and can hence be corrected by a simple phase
and amplitude correction factor. Thus the channel distortion correction entity within a
multicarrier receiver can be of significantly lower complexity than its counterpart within
a single carrier receiver when the system bandwidth is in excess of the coherence
bandwidth of the channel.
Orthogonal frequency division multiplexing (OFDM) is a modulation technique that is
based on FDM. An OFDM system uses a plurality of sub-carrier frequencies which are
orthogonal in a mathematical sense so that the sub-carriers' spectra may overlap
without interference due to the fact they are mutually independent. The orthogonality
of OFDM systems removes the need for guard band frequencies and thereby increases
the spectral efficiency of the system. OFDM has been proposed and adopted for many
wireless systems. It is currently used in Asymmetric Digital Subscriber Line (ADSL)
connections, in some wireless LAN applications (such as WiFi devices based on the
IEEE802.11a/g standard), and (of particular relevance to the present invention) in
wireless MAN applications such as WiMAX (based on the IEEE 802.16 standard).
OFDM is often used in conjunction with channel coding, an error correction technique,
to create coded orthogonal FDM or COFDM. COFDM is now widely used in digital

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telecommunications systems to improve the performance of an OFDM based system in
a multipath environment where variations in the channel distortion can be seen across
both subcarriers in the frequency domain and symbols in the time domain. The system
has found use in video and audio broadcasting, such as DVB and DAB, as well as
certain types of computer networking technology.
In an OFDM system, a block of N modulated parallel data source signals is mapped to
N orthogonal parallel sub-carriers by using an Inverse Discrete or Fast Fourier
Transform algorithm (IDFT/IFFT) to form a signal known as an "OFDM symbol" in the
time domain at the transmitter. Thus, an "OFDM symbol" is the composite signal of all
N sub-carrier signals. An OFDM symbol can be represented mathematically as:

where Δf is the sub-carrier separation in Hz, Ts = 1/Δf is symbol time interval in
seconds, and cn are the modulated source signals. The sub-carrier vector in (1) onto
which each of the source signals is modulated C Cn, c = (c0, C1.CN-I) is a vector of N
constellation symbols from a finite constellation. At the receiver, the received time-
domain signal is transformed back to frequency domain by applying Discrete Fourier
Transform (DFT) or Fast Fourier Transform (FFT) algorithm.

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OFDMA (Orthogonal Frequency Division Multiple Access) is a multiple access variant
of OFDM. It works by assigning a subset of sub-carriers to an individual user. This
allows simultaneous transmission from several users leading to better spectral
efficiency. However, there is still the issue of allowing bi-directional communication,
that is, in the uplink and download directions, without interference.
In order to enable bi-directional communication between two nodes, two well known
different approaches exist for duplexing the two (forward or download and reverse or
uplink) communication links to overcome the physical limitation that a device cannot
simultaneously transmit and receive on the same resource medium. The first,
frequency division duplexing (FDD), involves operating the two links simultaneously but
on different frequency bands by subdividing the transmission medium into two distinct
bands, one for forward link and the other for reverse link communications. The second,
time division duplexing (TDD), involves operating the two links on the same frequency
band, but subdividing the access to the medium in time so that only the forward or the
reverse link will be utilizing the medium at any one point in time. Both approaches
(TDD & FDD) have their relative merits and are both well used techniques for single
hop wired and wireless communication systems. For example the IEEE802.16
standard incorporates both an FDD and TDD mode. IEEE std 802.16-2004 "Air
Interface for Fixed Broadband Wireless Access Systems" is hereby incorporated by
reference in its entirety.
In a single-hop communication system in which communication takes place directly
between an MS/SS and a BS, a network entry procedure is followed by the MS/SS in
conjunction with the BS. However, the known network entry procedure is not sufficient

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for a multi-hop system in which communication between the BS and MS/SS takes
place via one or more relay stations RS. There is consequently a need for an improved
network entry procedure applicable in such a case.
Summary of the Invention
According to a first aspect of the present invention, there is provided a transmission
method for use in a wireless communication system, the system comprising a source
apparatus, a destination apparatus and an intermediate apparatus, the source
apparatus and destination apparatus being arranged to transmit and receive
information via the intermediate apparatus, at least the source apparatus being
arranged to perform a network entry process in order to connect to the system, the
method comprising: in the intermediate apparatus, determining whether the source
apparatus has initiated a network entry process with the intermediate apparatus and if
so, notifying the destination apparatus thereof whilst continuing to conduct the network
entry process with the source apparatus; and in the destination apparatus, responding
to said notification with a return message to the intermediate apparatus, said return
message being used to facilitate completion of the network entry process.
The invention is further defined in the independent claims, to which reference should
now be made. Advantageous embodiments are set out in the sub claims.
Embodiments of the invention provide a communication method, communication
system and intermediate apparatus (e.g., relay stations RS) employing a novel protocol
adopted as a network entry procedure followed by the BS and RS, to enable entry of a

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legacy MS or SS into a relaying enabled communication network. The protocol
involves decentralised control where the RS can manage the entire process. The
protocol is based on an adaptation of the current network entry procedure followed in
the IEEE802.16 standard and is specifically designed for the case when a RS transmits
synchronisation and broadcast control information (i.e. preamble and MAP).
The present invention also embraces computer software (which may be stored on a
computer-readable recording medium) for executing the novel protocol on a RS, or on
a MS/SS acting as an RS.
Brief Description of the Drawings
Preferred features of the present invention will now be described, by way of example,
with reference to the accompanying drawings, in which:-
Figure 1 shows a single-cell two-hop wireless communication system;
Figure 2 shows applications of relay stations RS;
Figure 3 shows standard MS network entry procedure; and

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Figure 4 shows an RS management procedure during an MS ranging process in a
relay enabled network, embodying the invention.
Detailed Description
In legacy single hop systems (e.g. 802.16-2004 and 802.16e-2005), standard network
entry procedures already exist to support entry of an MS or SS into a communication
network. However, when the network is modified to support relaying functionality, of
which a legacy MS or SS has no knowledge, a modified network entry procedure is
required from the network point of view to facilitate fast and efficient support of MS/SS
network entry.
This invention provides a protocol that is intended to be adopted as the modified
network entry procedure from the network point of view, i.e. adopted in the RS and BS.
In particular it is designed with application to the IEEE802.16 standard in mind and
requires no changes to the procedure from the MS or SS point of view. It is also
designed for the case of non-transparent relaying where the RS is able to transmit a
preamble and broadcast control information and hence has the capability to manage
the process locally (i.e. distributed control) and hence minimise the latency that would
otherwise be associated with relaying.
Figure 3 illustrates the network entry procedure described in the IEEE802.16 standard
which supports network entry of an MS or SS into a single-hop communication system.

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Here, it is assumed that any RS with which the MS is communicating during the
network entry procedure is already known to the network (incidentally, in this
specification, the terms "network" and "system" are used interchangeably). For
example, the RS may have already completed entry into the network following a
separate procedure, such as the one described in the applicant's UK application no.
0616475.0, the disclosure of which is hereby incorporated by reference. It is also
assumed that, as the network is required to support legacy users, the MS or SS still
follows the same network entry procedure from its point of view, as illustrated in Figure
3. However, the procedure followed by the RS is defined here and the one followed by
the BS is modified from that followed for the case of a single hop network. For ease of
explanation, a two-hop configuration as in Fig. 1 will be considered although the
present invention is not limited to this.
Scan for Downlink Channel
During this stage the MS/SS scans for preamble transmissions which may be
originating from either BSs or RSs. Once all potential preambles are detected, the MS
will select which channel it wishes to use from the available set of channels, in line with
the standard procedure. It will then synchronise its receiver with the transmitter.
Note that no additional operations are required beyond those in the existing single hop
system.
Obtain Uplink Parameters
During this stage the MS/SS obtains uplink parameters which includes location of the
uplink control information transmission region that will be used by the MS/SS in the

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next stage. This information will be generated by the BS or RS that the MS/SS is
attempting to connect to.
Ranging & Automatic Adjustments
The MS/SS will transmit a ranging code or ranging message, as defined in the
IEEE802.16 standard, as a form of identification information to identify itself to the
network. (Incidentally, the term "ranging message" is more correct when OFDM is
being used, and "ranging code" more appropriate to OFDMA, but in the following
description "ranging code" is used for both). It is possible that a number of receivers in
the multi-hop network receive this transmission. This code will be directed towards the
preferred receiver based on the downlink channel selected.
The receiver of the ranging code will then generally attempt to detect the ranging code
independently as the RS appears like a BS to the MS. However, as it is likely that the
RS will need to ensure that the BS and the BS to RS air interface can support this new
connection, some mechanism will be needed within the system to facilitate this. Three
alternative such mechanisms are:
1. The ranging request is relayed back to the BS from the RS, setting the
transmission power accordingly; or the detection is performed in RS but
detection information is relayed to the BS. However, due to the frame
structure associated with this type of system and the fact that any response
messages are required to come via the RS, both of these approaches will
incur extra latency from the view point of the MS/SS. Hence this method is

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not preferred for a performance point of view, however it keeps the
complexity to a minimum in the RS so is advantageous in this sense.
2. The BS informs the RS of a detection threshold and the RS manages the
ranging process until the threshold is met, generating any feedback
information locally. However, the final ranging response with the completion
method still has to be relayed from the BS, incur some extra latency. This
method provides a lower latency solution with the requirements of increased
complexity when compared with the mechanism proposed in 1.
3. (Preferred Mechanism): The RS completely manages the ranging process
locally. However, to ensure that the BS can support the connection, as
soon as it has knowledge of the MS attempting to enter the network through
detecting the ranging code for the first time, it then informs the BS that a
user is attempting network entry. Whilst the RS manages the ranging
process, it effectively pipelines in parallel a second "ranging process"
relating to this connection over the RS to BS link, thereby minimising
latency. This second "ranging process" is a process conducted by the RS
with the BS on behalf of the MS, and does not require a ranging code of its
own. The BS will then inform the RS whether the connection can be
supported, and also inform the RS of any specific information regarding the
connection type, service level, etc that can be offered over the composite
link. The RS can then interpret the information, passing on any relevant
elements to the MS/SS, or use it to determine whether to continue with the
ranging process. The RS may also request specific information from the BS

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that it will require to include in its successful ranging or any continue ranging
message. This third mechanism is preferred in terms of network
performance due to the fact it provides highest efficiency by running the
ranging and network entry process over the two links independently,
however it requires greatest complexity in the RS.
The procedure described in paragraph 3 is illustrated in Figure 4. Here, (100) indicates
the first message sent to the RS (or BS) by the MS or SS that is attempting to enter the
network through the RS. If the RS detects (100) then in the same frame (or at a later
instant) it sends a message (200) to the BS to request any information that is required
to support this process and also inform the BS of the arrival of (100). The RS will then
respond to the MS/SS with an appropriate message (300) which could be for example
a continue message and include information to the MS/SS such as adjustments to
make to its next transmission. The BS will also respond to (200) to acknowledge and
provide any of the requested information in (200), as shown with (400).
At some point later in time the MS/SS may transmit another message (500). If this is
still not sufficient from the RS perspective it may respond with another continue and
adjustment message such as (300). However, once it eventually receives a sufficient
message (500) the RS will conclude the ranging process. At this point it will notify the
BS with a message (600) and may also request information required for the following
stages of network entry in another message (700). The RS will then inform the MS/SS
of successful completion of the ranging process through another message (800).

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Note that in the case the first transmission from the MS/SS (100) is sufficient from the
RS point of view then the messages between the RS and BS will still be exchanged
(i.e. (200)(400)(600)(700)), however the RS and MS will obviously skip messages (300)
and (500).
Alternatively, in a multi-hop configuration, multiple RS may be interposed in the
communication path between the MS/SS and BS. In such a case, the above procedure
is modified to include one RS receiving, and/or relaying, a ranging code or detection
information from/to another RS, so that more than two process will occur in parallel,
independently managed by the respective RS.
In the above description, it is assumed that the network could consist of some legacy
BS (i.e., base stations operating in compliance with existing protocols) and some
relaying enabled BS (i.e., base stations operating in accordance with the present
invention). It is also assumed that a relaying enabled BS may be operating in a legacy
mode until it receives a request from an RS for it to enter the network. The reason the
BS may operate in such a mode would be to preserve transmission resources by not
having to broadcast relay specific information when there are no relays benefiting from
the transmission.
Remaining network entry processes
Once the RS has knowledge of the MS entering the network, it is possible for it to
completely manage the remaining steps in the network entry process. It can then
source information or inform the BS of the status of the procedure as and when

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required in such a way that the process between the RS and MS is optimised in terms
of not introducing any extra latency.
For example, assuming that the RS has undergone authorisation with the BS, the RS
can locally manage the authorisation process, informing the BS of the status, and
sourcing any centrally held information as required from any centrally located servers
that manage the authorisation within the network.
As described above, the present invention can provide the following effects:
Defines a ranging and network entry procedure that effectively consists of two or
more (depending on number of links) processes occurring in parallel and
independently managed by the RS to which the connection is being sought;
Minimises the latency that would be associated with network entry due to the local
management of the process;
Provides a scalable solution that enables a system to support potentially a large
number of hops with no significant or, at worst, limited impact on network entry
performance.
Thus, an embodiment of the present invention can provide a transmission method for
use in a wireless communication system, the system comprising a subscriber station,

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base station and intermediate apparatus in the form of one or more relay stations, the
subscriber station and the base station being arranged to transmit and receive
information via the intermediate apparatus, at least the subscriber station being
required to perform a network entry process in order to connect to the system. The
method comprises, in the intermediate apparatus, determining whether the subscriber
station has initiated a network entry process with the intermediate apparatus, for
example by receiving a ranging code from the subscriber station. Upon such a
determination, the intermediate apparatus notifies the base station of the fact whilst
continuing to conduct the network entry process with the subscriber station. The base
station responds to this notification with a return message to the intermediate
apparatus. This return message is part of a guidance process conducted from the
base station to the intermediate apparatus so that the intermediate apparatus can
manage completion of the network entry process. The method has particular relevance
to multi-hop wireless systems based on standards such as IEEE802.16.
Embodiments of the present invention may be implemented in hardware, or as
software modules running on one or more processors, or on a combination thereof.
That is, those skilled in the art will appreciate that a microprocessor or digital signal
processor (DSP) may be used in practice to implement some or all of the functionality
of a transmitter embodying the present invention. The invention may also be embodied
as one or more device or apparatus programs (e.g. computer programs and computer
program products) for carrying out part or all of any of the methods described herein.
Such programs embodying the present invention may be stored on computer-readable
media, or could, for example, be in the form of one or more signals. Such signals may
be data signals downloadable from an Internet website, or provided on a carrier signal,
or in any other form.

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A program embodying the invention could also be used to add the functionality of the
RS as described above to a MS/SS having suitable hardware.

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CLAIMS
1. A transmission method for use in a wireless communication system, the system
comprising a source apparatus, a destination apparatus and an intermediate
apparatus, the source apparatus and destination apparatus being arranged to transmit
and receive information via the intermediate apparatus, at least the source apparatus
being arranged to perform a network entry process in order to connect to the system,
the method comprising:
in the intermediate apparatus, determining whether the source apparatus has
initiated a network entry process with the intermediate apparatus and if so, notifying the
destination apparatus thereof whilst continuing to conduct the network entry process
with the source apparatus; and
in the destination apparatus, responding to said notification with a return
message to the intermediate apparatus, said return message being used to facilitate
completion of the network entry process.
2. The transmission method according to claim 1 wherein said network entry
process includes one or more ranging attempts from the source apparatus to the
intermediate apparatus.
3. The transmission method according to claim 2, wherein following a successful
ranging attempt, said intermediate apparatus manages the rest of the network entry
process with the source apparatus.

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4. The transmission method according to any preceding claim wherein said
notification from the intermediate apparatus to the destination apparatus is part of a
guidance process for network entry of the source apparatus, conducted between the
destination apparatus and the intermediate apparatus in parallel with, and
independently from, said network entry process conducted by the intermediate
apparatus with the source apparatus.
5. The transmission method according to any preceding claim wherein said return
message from the destination apparatus to the intermediate apparatus informs the
intermediate apparatus of whether the connection can be supported.
6. The transmission method according to any preceding claim, wherein said return
message from the destination apparatus to the intermediate apparatus informs the
intermediate apparatus of a connection type and/or service level available to the source
apparatus via the intermediate apparatus.
7. The transmission method according to claim 6 wherein the intermediate
apparatus forwards information, derived from said return message, to the source
apparatus.
8. The transmission method according to claim 6 or 7 wherein the intermediate
apparatus uses said return message to determine whether to continue with the network
entry process.
9. The transmission method according to claim 6, 7, or 8 wherein the intermediate
apparatus uses said return message to request specific information from the source
apparatus.

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10. The transmission method according to any preceding claim, wherein the source
apparatus is a subscriber station.
11. The transmission method according to any preceding claim, wherein the source
apparatus is a mobile terminal.
12. The transmission method according to any preceding claim, wherein the
destination apparatus is a base station.
13. The transmission method according to any preceding claim, wherein the
intermediate apparatus is a relay station arranged in a two-hop configuration between
the source apparatus and the destination apparatus.
14. The transmission method according to any of claims 1 to 12, wherein the
intermediate apparatus is constituted by a plurality of relay stations arranged in a multi-
hop configuration between the source apparatus and the destination apparatus, a first
of the relay stations detecting the initiation of the network entry process by the source
apparatus and relaying said notification to another of the relay stations for forwarding
to the destination apparatus.
15. A wireless communication system comprising a source apparatus, a destination
apparatus and an intermediate apparatus, the source apparatus and destination
apparatus being arranged to transmit and receive information via the intermediate
apparatus, at least the source apparatus being arranged to perform a network entry
process in order to connect to the system, wherein:

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the intermediate apparatus includes determining means for determining whether
the source apparatus has initiated a network entry process with the intermediate
apparatus, notifying means responsive to an output of the determining means to notify
the destination apparatus of a network entry process being initiated, and managing
means for conducting the network entry process with the source apparatus
concurrently with operation of the notifying means; and
the destination apparatus includes means for responding to said notification
with a return message to the intermediate apparatus, said return message being used
by said managing means to facilitate completion of the network entry process.
16. The system according to claim 15 wherein said network entry process includes
one or more ranging attempts from the source apparatus to the intermediate apparatus.
17. The system according to claim 16, wherein the managing means of the
intermediate apparatus is responsive to a successful ranging attempt to manage the
rest of the network entry process with the source apparatus.
18. The system according to any of claims 15 to 17 wherein said notification from the
intermediate apparatus to the destination apparatus is part of a guidance process for
network entry of the source apparatus conducted between the destination apparatus
and the intermediate apparatus, and said managing means is configured to conduct
said guidance process in parallel with, and independently from, conducting said
network entry process with the source apparatus.
19. The system according to any of claims 15 to 18 wherein the destination
apparatus is arranged to send said return message to the intermediate apparatus
informing the intermediate apparatus of whether the connection can be supported.

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20. The system according to any of claims 15 to 19, wherein the destination
apparatus is arranged to send said return message to inform the intermediate
apparatus of a connection type and/or service level available to the source apparatus
via the intermediate apparatus.
21. The system according to claim 20 wherein the intermediate apparatus is
arranged to forward information, derived from said return message, to the source
apparatus.
22. The system according to claim 20 or 21 wherein the managing means of the
intermediate apparatus is responsive to said return message to determine whether to
continue with the network entry process.
23. The system according to claim 20, 21 or 22 wherein the managing means of the
intermediate apparatus is responsive to said return message to request specific
information from the source apparatus.
24. Intermediate apparatus for use in a wireless communication system, the system
having a source apparatus and a destination apparatus arranged to transmit and
receive information via the intermediate apparatus, the system requiring at least the
source apparatus to perform a network entry process in order to connect to the system,
wherein the intermediate apparatus includes:
determining means for determining whether the source apparatus has initiated
a network entry process with the intermediate apparatus;
notifying means responsive to an output of the determining means to notify the
destination apparatus of a network entry process being initiated; and

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managing means for managing the network entry process with the source
apparatus simultaneously with operation of the notifying means and responsive to a
reply, sent from said destination apparatus in response to said notification, to complete
the network entry process with the source apparatus by using information contained in
said reply.
25. Intermediate apparatus according to claim 24 in the form of a single relay station
for use in a two-hop configuration with the source apparatus and the destination
apparatus.
26. Intermediate apparatus according to claim 24 in the form of a plurality of relay
stations for use in a multi-hop configuration between the source apparatus and the
destination apparatus, each relay station including said determining means, said
notifying means, and said managing means,
said notifying means also being responsive to a notification from another one of
the relay stations, and arranged to notify either the destination apparatus, or an
upstream relay station if any, of the network entry process being initiated by the source
apparatus; and
said managing means also being responsive from a reply received via the
upstream relay station if any, either to complete the network entry process with the
source apparatus by using information contained in said reply or to forward said
information to a downstream relay station if any.
27. A computer-readable recording medium storing a computer program which, when
executed by intermediate apparatus in a wireless communication system having a
subscriber station and a base station each arranged to transmit and receive information
via the intermediate apparatus and requiring at least the subscriber station to perform a

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network entry process in order to connect to the system, provides the intermediate
apparatus with the functions of:
determining means for determining whether the subscriber station has initiated
a network entry process with the intermediate apparatus;
notifying means responsive to an output of the determining means to notify the
base station of a network entry process being initiated; and
managing means for managing the network entry process with the subscriber
station simultaneously with operation of the notifying means and responsive to a reply,
sent from the base station in response to said notification, to complete the network
entry process with the subscriber station by using information contained in said reply.
28. The computer-readable recording medium according to claim 27 wherein the
computer program allows the intermediate apparatus to be constituted by one or more
relay stations.
29. The computer-readable recording medium according to claim 27 wherein the
computer program allows the intermediate apparatus to be constituted by one or more
further subscriber stations.
30. A transmission method substantially as hereinbefore described with reference to
the accompanying drawings.
31. A wireless communication system substantially as hereinbefore described with
reference to the accompanying drawings.
32. A computer-readable recording medium storing a computer program substantially
as hereinbefore described with reference to the accompanying drawings.

A transmission method for use in a wireless communication system, the system
comprising a subscriber station, base station and intermediate apparatus in the form of
one or more relay stations, the subscriber station and the base station being arranged
to transmit and receive information via the intermediate apparatus, at least the
subscriber station being required to perform a network entry process in order to
connect to the system. The method comprises, in the intermediate apparatus,
determining whether the subscriber station has initiated a network entry process with
the intermediate apparatus, for example by receiving a ranging code from the
subscriber station. Upon such a determination, the intermediate apparatus notifies the
base station of the fact whilst continuing to conduct the network entry process with the
subscriber station. The base station responds with a return message to the
intermediate apparatus, as part of a guidance process conducted from the base station
to the intermediate apparatus so that the intermediate apparatus can manage
completion of the network entry process. The method has particular relevance to multi-
hop wireless systems based on standards such as IEEE 802.16 (WiMAX).