WO2012112126A1

WO2012112126A1 - Neighbor discovery in a cellular mobile communication system

Info

Publication number: WO2012112126A1
Application number: PCT/SG2012/000049
Authority: WO
Inventors: Haiguang Wang; Anh Tuan Hoang; Jaya Shankar s/o PATHMASUNTHARAM; Zhongding Lei; Shoukang ZHENG
Original assignee: Agency For Science, Technology And Research
Priority date: 2011-02-17
Filing date: 2012-02-17
Publication date: 2012-08-23

Abstract

The present invention is directed to a communication terminal of a cellular mobile communication system, the communication terminal comprising a transceiver configured to broadcast a message indicating to at least one other communication terminal of the cellular mobile communication system that receives the message that the communication terminal is a neighbor of the at least one other communication terminal. The present invention is also directed to a communication terminal comprising a transceiver configured to receive a broadcast message from at least one other communication terminal indicating that the communication terminal is a neighbor of the at least one other communication terminal. A method of determining a neighbor for a communication terminal is also disclosed.

Description

Neighbor Discovery in a Cellular Mobile Communication System

Cross-Reference To Related Application

[0001] This application makes reference to and claims the benefit of priority of the applications for "A Neighbor and Path Discovery Method for IEEE 802.16η Network" filed on February 17, 2011, "A Method To Support HR-MS Forwarding In 802.16 Networks" filed on March 3, 2011, and "Coverage Extension and Alternative Path Management in 802.16 HR-networks" filed on March 1 1, 2011, all with the Intellectual Property Office of Singapore, and there duly assigned application numbers 201101131-9, 201101534-4, and 201101771-2, respectively.

Technical Field

[0002] Various embodiments generally relate to the field of neighbor discovery in cellular mobile communication systems, in particular, neighbor discovery in OFDMA- based networks like an LTE/LTE-Advanced network or an IEEE 802.16e/m/n network.

Background

[0003] The IEEE 802.16 standard contains a series of wireless broadband standard and defines a point-to-multi-point (PMP) communication protocol for the Metropolitan Area Network (MAN). The IEEE 802.16 standard was originally defined for wireless broadband access but has later evolved to a standard that supports cellular wireless communication. This standard has been adopted by International Telecommunication Union (ITU) as a formal 3G technology and now, after being enhanced by IEEE 802.16m, becomes one of the approved ITU 4G technologies. An organization named as WiMax Forum has been setup for marketing the IEEE 802.16 technology. Currently, IEEE 802.16 technology has been deployed for mobile communication in a number of countries, including USA, Korea, Taiwan, Indonesia and Australia, etc.

[0004] Figure 1 shows a schematic representation of the protocol architecture 100 of the IEEE 802.16 technology. The 802.16 standard mainly defines a Media Access Control (MAC) layer 102 and a Physical (PHY) layer 104 for communication. The MAC layer is further divided into Convergence Sub-layer (CS) 106 and MAC common sub-layer 108.

[0005] With the 802.16 system, a mobile station (MS) can only send and receive data to and from a base station (BS) or relay station (RS). It can work in both Time Division Duplex (TDD) and Frequency Division Duplex (FDD) modes. In FDD mode, downlink (from the BS to the MS) and uplink (from the MS to the BS) work on different frequency. Both the BS and MS can transmit and receive simultaneously. While in the TDD mode, the downlink and uplink are separate in time. BSs and MSs can only either transmit or receive at a given time epoch.

[0006] With the 802.16 standard, i.e. 802.16-2009, the channel access time is divided into frames and the duration of frame may vary from about 2 ms to about 20 ms. Figure 2(a) shows an example of a 802.16 frame structure in the TDD mode.

[0007] It can be observed that a frame 200 is divided into downlink subframes 202 and uplink subframes 204. The duration of a frame is usually fixed but the duration of a sub- frame may vary from time to time.

[0008] The frame structure may be changed significantly in the 802.16m amendment. Figure 2(b) shows a typical frame structure defined in the 802.16m. In the 802.16m, the channel access time is first divided into super- frames 210, which are 20 ms long. Each super- frame consists of four frames 212. The duration of a frame 212 is 5 ms. The frame 212 is further divided into a number of sub-frames 214. Each sub-frame 214 contains 5 - 8 OFDMA (Orthogonal Frequency-Division Multiple Access) symbols 216. Some of the sub-frames 214 are used for downlink (DL) transmission and some of the subframes 214 are used for uplink (UL) transmission.

[0009] The 802.16 system uses OFDMA technology in communication. Figure 3 shows an example of how the 802.16 system transmits data with OFDMA technology. The radio spectrum 300 is divided into sub-channels 302 and sub-carriers 304. Multiple MSs can transmit to or received from the BS at the same time.

[0010] Recently, the IEEE 802.16 working group established a new task group, 802.16η, to enhance the reliability of the 802.16 system. The purpose is to allow the MSs in the network to continue their communication in case the network infrastructure is degraded, for example, when a BS or an RS stop functioning or when a network is cut off from the infrastructure backhaul. The 802.16 system with enhanced features can be used for smart grid, machine-to-machine communication, public safety, airport and maritime communication. All these usage scenarios require the system to provide a higher reliability.

[0011] In order to enhance system reliability, there is a need to provide OFDMA-based networks that can efficiently acquire topology/neighborhood information, which is essential for radio-resource reuse, routing-path optimization, and fast network recovery.

[0012] In the IEEE 802.16 standard, neighbor discovery has been addressed in three versions, namely IEEE 802.16-2004, IEEE 802.16e and IEEE 802.16j.

[0013] In IEEE 802.16-2004, the MAC layer can work in two modes, the Point-to-Multi- Point mode and the mesh mode. Neighbor discovery is included in the mesh node. The MAC in PMP and Mesh mode are totally different and the mesh mode was later removed from the standard to give the IEEE 802.16d standard.

[0014] In the IEEE 802.16e, neighbor discovery is also included in the design. However, in the IEEE 802.16e standard amendment, the neighbor refers to the neighboring BS. The BS periodically schedule the MSs associated to it, scanning the signal from neighboring BS and reporting to it.

[0015] In the IEEE 802.16j standard amendment, since it is designed for supporting Mobile Multi-hop Relay (MMR), neighbor discovery for relay stations has been proposed in the amendment. It requires the BS to transmit the signals (relay-ambles) for neighbor discovery while other RSs may be scheduled to capture this signal and report to the BS.

[0016] Thus, there is a need to provide neighbor discovery, in particular, in a cellular mobile communication system of the IEEE 802.16η standard. Summary of the Invention

[0017] In a first aspect, the present invention relates to a communication terminal of a cellular mobile communication system, the communication terminal comprising a transceiver configured to broadcast a message indicating to at least one other communication terminal of the cellular mobile communication system that receives the message that the communication terminal is a neighbor of the at least one other communication terminal.

[0018] According to a second aspect, the present invention also relates to a communication terminal of a cellular mobile communication system, the communication terminal comprising a transceiver configured to receive a broadcast message from at least one other communication terminal of the cellular mobile communication system indicating that the communication terminal is a neighbor of the at least one other communication terminal.

[0019] In accordance to a third aspect, the present invention relates to a base station operable with a plurality of communication terminals of a cellular mobile communication system, the base station comprising a determiner configured to determine a neighbor discovery type for performing neighbor discovery on the plurality of communication terminals; and an indicator generator configured to generate an indicator indicating the neighbor discovery to perform on the plurality of communication terminals depending on the determined neighbor discovery type.

[0020] According to a fourth aspect, the present invention relates to a method of determining a neighbor for a communication terminal of a cellular mobile communication system, the method comprising receiving an indicator from a base station indicating a neighbor discovery type; broadcasting from the communication terminal a message based on the indicator; and determining based on the neighbor discovery type whether at least one other communication terminal in the communication system is a neighbor of the communication terminal if the at least one other communication terminal receives the message. Brief Description of the Drawings

[0021] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which:

[0022] Figure 1 shows a schematic representation of the protocol architecture of the IEEE 802.16 technology;

[0023] Figure 2(a) shows an example of a 802.16 frame structure in the TDD mode;

[0024] Figure 2(b) shows a typical frame structure defined in the 802.16m;

[0025] Figure 3 shows an example of how the 802.16 system transmits data with OFDMA technology;

[0026] Figure 4 shows a network reference model defined for the 802.16η network, in accordance to various embodiments;

[0027] Figure 5 shows a communication terminal performing neighbor discovery, in accordance to various embodiments;

[0028] Figure 6 shows a schematic block diagram of a communication terminal of a cellular mobile communication system, in accordance to various embodiments;

[0029] Figure 7(a) shows the scheduling of standard ranging operation in current 802.16m frame structure, in accordance to various embodiments;

[0030] Figure 7(b) shows network-discovery ranging being scheduled in a 802.16m frame structure, in accordance to various embodiments;

[0031] Figure 8 shows an example of preamble transmitting with respect to 802.16m, in accordance to various embodiments;

[0032] Figure 9 shows a flexible framework proposed to enable neighbor and path discovery to accelerate path discovery, in accordance to various embodiments;

[0033] Figure 10 shows a schematic representation of extending communication range with HR-MS, in accordance to various embodiments; [0034] Figure 11 shows an example of extended neighbor discovery subframe for FIRMS range extension, in accordance to various embodiments;

[0035] Figure 12 shows schematic block diagram of a base station operable with a plurality of communication terminals of a cellular mobile communication system, in accordance to various embodiments;

[0036] Figure 13 shows a schematic block diagram of a method of determining a neighbor for a communication terminal of a cellular mobile communication system, in accordance to various embodiments; and

[0037] Figure 14 shows an exemplary method for neighbor discovery in 802.16e based HR-networks.

Detailed Description

[0038] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, and logical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0039] In order that the invention may be readily understood and put into practical effect, particular embodiments will now be described by way of examples and not limitations, and with reference to the figures.

[0040] To enhance system reliability, the 802.16 specifications would have to be amended to allow the following features:

• Direct MS-to-MS communication

• MS forwarding control/data messages for another MS to/from infrastructure station

• Capability of multi-hop communication • Local forwarding

• Supporting for multi-path

• Neighbor discovery

• Relay source and sink data

[00411 Figure 4 shows a network reference model defined for the 802.16n network.

[0042] The most important communication scenario faced by the 802.16η network is that a base station or relay station may crash due to disaster or war. In such case, MSs (or referred to as high-reliability HR-MSs) 400 that implement the 802.16η features may change their respective role to a BS (or referred to as high-reliability HR-BS) 402 or RS (or referred to as high-reliability HR-RS) 404.

[0043] The design for the 802.16η system in neighbor and path discovery considers characteristics of the existing technology such as 802.16-2009, 802.16m and enhances the reliability of 802.16n system.

[0044] Neighbor discovery can be seen to be needed for three purposes in the IEEE 802.16η network. The first is for radio-resource reuse. In IEEE 802.16η, both the HR-RS and HR-MS, for example, the HR-RS 402 and HR-MS 400 of Figure 4, are allowed to relay data and may also support multi-hop relaying. Neighbor discovering will enable the HR-BS, for example, the HR-BS 404 of Figure 4, to reuse the radio resource. The second usage may be the path discovery and optimization. Neighbor discovery helps the HR-BS to know the topology of network and to make decision in determining routing paths for the nodes. Path discovery can also result in coverage extension. The HR-MS may be allowed to forward data and control messages for other HR-MSs. With neighbor discovery, HR-MSs, either associated or outside coverage, may be able to locate others that can provide the data and control message forwarding. The third purpose is for fast network recovery. By acquiring network topology and neighborhood information, nodes in the network can prepare for and react to infrastructure failure faster. Neighbor discovery advantageously provides as a core enabling function for the features listed for the 802.16 specifications, as described hereinabove.

[0045] Figure 5 shows an example of a communication terminal performing neighbor discovery according to an embodiment. In Figure 5, a communication system 500 is provided. A base station 502 or interchangably referred to as a HR-BS, for example, the HR-BS 404 in Figure 4, broadcasts an indicator 504 to communication terminals 506, 508, 510, 512. The communication terminals 506, 508, 510, 512 may comprise HR-MSs, for example, the HR-MSs 400 in Figure 4. Without limiting to the example as shown in Figure 5, the communication system 500 may comprise more than one base station. The indicator 504 indicates a neighbor discovery type as described herein.

[0046] Upon receiving the indicator 504, each communication terminal 506, 508, 510, 512 performs neighbor discovery based on the neighbor discovery type. An expanded view of encircled area 5000 shows the communication terminal 508 as an example performing neighbor discovery based on the neighbor discovery type. The communication terminal 508 broadcast a message 514 to other communication terminals 510, 512. The other communication terminal 510 receives the message and is therefore a neighbor of the communication terminal 508, establishing a communication link 516 therebetween. The other communication terminal 512 does not receive the message and is therefore not a neighbor of the communication terminal 508 and no communication link can be established therebetween.

[0047] In a first aspect, a communication terminal of a cellular mobile communication system is provided as shown in Figure 6. In Figure 6, the communication terminal 600 comprises a transceiver 602 configured to broadcast a message indicating to at least one other communication terminal of the cellular mobile communication system that receives the message that the communication terminal 600 is a neighbor of the at least one other communication terminal.

[0 48] For example, the communication terminal 600 may be the communication terminal 508 of Figure 5 and the cellular mobile communication system may be the communication system 500 of Figure 5.

[0049] In the context of various embodiments, the term "communication terminal" may refer to a machine that assists data transmission, that is sending and/or receiving data information. Accordingly, the communication terminal may also be generally referred to as a node. A communication terminal may be, for example but not limited to, a station, or a mobile station (MS), or a substation, or a port, or a mobile phone, or a cellular phone. (0050] In one embodiment, the communication terminal 600 may comprise a MS of the cellular mobile communication system. In other embodiments, the MS may be any of a Personal Digital Assistant (PDA), a cellular phone, a Personal Communication Service (PCS) phone, a Global System for Mobile (GSM) phone, a Wideband Code Division Multiple Access (WCDMA) phone, a Mobile Broadband System (MBS) phone, etc. The term 'MS' may interchangably be referred to as the term 'User Equipment (UE)', 'Subscriber Station (SS'), 'Mobile Subscriber Station (MSS)', 'mobile terminal', 'Advanced Mobile Station (AMS)', etc.

[0051] The plurality of communication terminals may be referred to as a plurality of stations.

[0052] In the context of various embodiments, the term "transceiver" refers to a combination transmitter/receiver. For example, a transceiver may be the transmitter and receiver combined into a single package. In general, a transceiver comprises both transmitting and receiving capabilities and functions.

[0053] The term "transmitting" may refer but not limited to sending out or broadcasting. In this context, a transmitter means a node that transmits voice or data service.

[0054] In the context of various embodiments, the term "broadcast" refers to sending out a message from one node, for example the communication terminal 600 of Figure 6, over an area, i.e. to all or multiple communication devices (e.g. using the same radio communication technology, e.g. according to the same communication standard, as the communication terminal or being part of the same communication network as the communication device) located in the area. As used herein, "multiple"communication devices may refer to a subset of communication terminals (or MSs) in the network.

[0055] As a further example, broadcast is when a single node is transmitting a message to all other nodes in a given address group. This broadcast can reach all hosts on the subnet, all subnets, or all hosts on all subnets. For example, based on the given address group, the BS can pick any subset of communication terminals (or MSs) to be the receiving communication terminals (or receiving MSs). [0056] Broadcast may be limited broadcast or direct broadcast. Limited broadcast refers to sending a message to all nodes on the same network segment. This broadcast is not forwarded to other network segments and so will only appear on one network segment.

[0057] As used herein, the term "network segment" refers to part of a network, on which all message traffic is common to all nodes, i.e. for example, a message is broadcast from one node on the segment and received by all others in the segment. Within a network segment, all message traffic may be broadcast via a same frequency/channel or a same group of freqencies/channels. The size of a segment may be defined by the amount of network traffic it carries.

[0058] Direct broadcast refers to sending a message to all hosts (nodes) on a network. The message may be forwardly directed on large networks. In some embodiments, "broadcast" may encompass "multicast", wherein in multicast, a transmission is made to a group of nodes on a network or system.

[0059] The term "message" refers to a signal or a communication signal. In the context of various embodiments, a message may be a short information sent from one entity (node), for example, the communication terminal 508 of Figure 5 or the communication terminal 600 of Figure 6, to at least another one entity (node), for example, the communication terminal 510, 512 of Figure 5. A message may be a packet or a cluster.

[0060] For example, a message may comprise precisely formatted data that is sent and received by nodes and may represent a request, report, or an event. The message may be comprised in or encoded in or indicated in another message or information or an indicator.

[0061] The message may comprise a message body, which is a section of a message that contains the contents of the message, and which may be of a predetermined structure. The message may also comprise a message header, which is an information structure in a message that precedes and identifies the information that follows within the message, and describes specifics about the message such as the properties of the message. The message may also refer to a data element encapsulated in a package of flags.

[0062] In various embodiments, the message may comprise a predefined sequence such as a Code Division Multiple Access (CDMA) ranging code or a preamble of a packet in a frame structure of a particular communication standard. For example, the particular communication standard may be the IEEE 802.16 communication standard.

[0063] As used herein, the term "preamble" is a sequence transmitted by a node that may be used by another node to differentiate nodes in a network or a subnet or a neighborhood. As a non-limiting example, the preamble may be a sequence transmitted by a base station that may be used by a mobile station to differentiate base stations in the neighborhood. The preamble may not be limited to the header or beginning part of an OFDM frame, but may cover the middle or the end or any part of the OFDM frame.

[0064] In various examples, the CDMA ranging code and the preamble may be HEX representations. The CDMA ranging code can also be refered to as a ranging sequence or a ranging preamble.

[0065] As used herein, the term "indicating" includes, but not be limited by, specifying, showing, implying, revealing, notifying, publishing, and registering.

[0066] In the context of various embodiments, the term "receive" may interchangably be referred but not limited to as listen, or collect, or detect. For example, "receive" may further include to determine that the received message is correctly or incorrectly obtained. When correctly obtained, the received message is identical or substantially the same as the transmitted message. Such determining of a correct or incorrect message may be performed by error detections, for example, cyclic redundancy check (CRC). Further to this, the correctly obtained message may also need to contain an absolute power level or a relative power level to noise and interference above a particular threshold. The correctly obtained message may also need to indicate a time and or frequency offset below a particular threshold. In this context, a receiver means a node or terminal that receives voice or data service.

[0067] The term "neighbor" denotes another communication terminal located within the transmission range of a communication terminal, and the term "transmission range" denotes coverage within one hop or two hops of a communication terminal. In some examples, the transmission range may be of multiple hops of the communication terminal or may be defined by a predetermined geographic area. In this context, a "hop" means a journey for which a message is sent from one communication terminal to another communication terminal or node in the network. One hop may refer to a value of distance limitation and two hops may therefore refer to twice the value of this distance limitation.

[0068] In various embodiments, a communication terminal has broadcasting capabilities facilitated by a transceiver of the communication terminal. The transceiver broadcasts a message to at least one other communication terminal of a cellular mobile communication system. If the at least one other communication terminal receives the message, the communication terminal broadcasting the message is regarded as a neighbor of the at least one other communication terminal. The communication terminal may also constitue a neighbor of the at least one other communication terminal by meeting other or additional conditions. Examples of such conditions may be for the message to be merely detected, that is regardless of whether it is the correct or incorrect message; or for the message to be correctly received, which may then require error detection to be carried out.

[0069] As an example, a neighbor of the communication terminal 508 of Figure 5 may be the other communication terminal 510 of Figure 5.

[0070] In a second aspect, a communication terminal of a cellular mobile communication system is provided, the communication terminal comprising a transceiver configured to receive a broadcast message from at least one other communication terminal of the cellular mobile communication system indicating that the communication terminal is a neighbor of the at least one other communication terminal. For example, the communication terminal may be the communication terminal 600 of Figure 6 or the communication terminal 510 of Figure 5. The at least one other communication terminal may be the communication terminal 508 of Figure 5. The transceiver may be the transceiver 602 of Figure 6.

[0071] In the context of various embodiments, the terms "receive", "communication terminal", "indicating" and "neighbor" are as defined above.

[0072] As used herein, the term "broadcast message" refers to a message that has been broadcast by a communication terminal. The terms "broadcast" and "message" are as defined above. [0073] As used herein, the term "commumcation system" broadly refers to a system used to communicate information. In this context, the communication system is a cellular mobile communication system comprising transmitting and receiving elements for communicating information.

[0074] In various embodiments, the communication system may work in accordance with a IEEE 802.16 communication standard.

[0075] The communication system may comprise a communication network for providing a communication connection between the communication terminal and the at least one other communication terminal via at least one base station of the commumcation network.

[0076] In the context of various embodiments, the term "commumcation network" generally refers to a wireless communication network. For example, the communication network may be a IEEE 802.16 network. The term "communication network" also includes any method or medium for transmitting (or receiving) information from one node to another. A communication network is formed via a communication connection among nodes. In some embodiments, the terms "communication network" and "commumcation system" may be interchangably used.

[0077] A "communication connection" may generally refer to a link to provide information transfer between one node and another node. The link may, for example, be the link 516 of Figure 5. In this context, the node may refer to a communication terminal or a base station. For example, a communication connection may also comprise a link from one communication terminal to a base station, or vice versa. In another example, a communication connection may comprise a link from one communication terminal to a base station to another communication terminal. In a different example, a communication connection may comprise a link from a base station to one communication terminal to another communication terminal. Vice versa, a communication connection may also comprise a link from one communication terminal to another commumcation terminal to a base station. The commumcation connection may be wireless. The communication connection may provide unidirectional or bidirectional information transfer. [0078] As used herein, the term "via" may refer to "through" or "involving". For example, a communication connection may be provided between the communication terminal and the at least one other communication terminal through at least one base station of the communication network. This means that there is a sequential order where the information is transferred from the communication terminal to the at least one base station of the communication network and subsequentially to the at least one other communication terminal.

[0079] In other examples, a communication connection may be provided between the communication terminal and the at least one other communication terminal involving at least one base station of the communication network. This means that the information is transferred, in no particular order or arrangement, sequentially among the communication terminal, the at least one other communication terminal and the at least one base station. As a non-limiting example, the information may be transferred from the at least one base station of the communication network to the communication terminal and subsequentially to the at least one other communication terminal.

[0080] In the context of various embodiments, the term "base station" (BS) refers to a node of a network, which communicates directly with the communication terminal, for example, the MS.

[0081] It may be apparent that, in a network comprised of a plurality of network nodes including a BS, various operations performed for communication with an MS may be performed by the BS, or network nodes other than the BS. The term 'BS' may interchangably referred to as the term 'fixed station', "Node B', 'eNode B (eNB)', 'access point', 'Advanced Base Station (ABS), etc.

[0082] For example, the BS may be the base station 502 of Figure 5. In this context, the

MS may be the communication terminal 506, 508, 510, 512 of Figure 5.

[0083] In other embodiments, the message may be broadcast without being communicated via the at least one base station of the communication network.

[0084] For example, the message may be the message 514 of Figure 5 broadcast by the communication terminal 508 of Figure 5 to other communication terminal 510, 512 of

Figure 5 without being communicated via the base station 502 of Figure 5. [0085] As used herein, the term "communicated" respectively refers to transferred, or transmitted, or received.

[0086] In various embodiments, the message may broadcast without the communication network being involved in the broadcast of the message.

[0087] For example, the message may be broadcast directly from the communication terminal to the other communication terminals without going through the network (e.g. a base station, or generally the radio access network) of the cellular communication system. In contrast, the example of a user sending a message from a mobile phone via the network which is addressed to a plurality of recipients, would be considered to have the message being broadcast with the communication network being involved in the broadcast of the message.

[0088] In various embodiments, the communication terminal may receive from the at least one base station an indicator indicating that neighbor discovery is performed on the communication terminals depending on a neighbor discovery type determined by the at least one base station, and broadcasts the message accordingly.

[0089] As used herein, the term "indicator" refers to an information related to the message as defined above. For example, the indicator may contain the message itself or may provide guidance or instructions to the communication terminal receiving the indicator as to the formulation or selection and/or scheduling of the appropriate message to be broadcast.

[0090] The term "neighbor discovery" refers to the process by which an HR-MS learns the existence of other HR-MSs within its communication range and may subsequently report the findings to HR-BS. This may be achieved by a HR-BS scheduling an HR-MS to broadcast a message for other HR-MSs to detect and, if possible, estimate the link conditions from the transmitting HR-MS.

[0091] In one example, the HR-BS may schedule an HR-MS to broadcast preamble sequences similar to that broadcast by the HR-BS and a HR-RS. This may be followed by network/neighborhood information for the receiving HR-MSs to obtain two-hop neighborhood information. As used herein, the term "HR-RS" or "relay station" refers to a wireless node that relays communications, either directly, or indirectly through one or more other RSs, between a network controller and a subscriber station, which is associated with the network controller and whose communications with the network controller are largely scheduled by the network controller.

[0092] In another example, the HR-BS may schedule an HR-MS to broadcast ranging sequences similar to that used for uplink (UL) ranging between the HR-MS and the HR- BS. A receiving HR-MS, by processing the received ranging sequence, may be able to estimate time, frequency, and power offsets with respect to the transmitting HR-MS.

[0093] In another example, the HR-BS may schedule an HR-MS to broadcast sounding sequences similar to that used for closed-loop link-adaptation between the HR-BS and the HR-MS. Examples of sounding sequences may be Golay sequences.

[0094] When an HR-MS broadcasts a predetermined sequence, other HR-MSs may try to listen, process, and report the information obtained to the HR-BS.

[0095] Neighbor discovery may be used for purposes such as MS direct communication, path discovery and optimization, interference-mitigation, network-recovery preparation and operation of HR-MS forwarding to network (FTN).

[0096] In the context of various embodiments, the term "neighbor discovery type" refers to an identifier for a predetermined procedure of performing neighbor discovery.

[0097] In various embodiments, the neighbor discovery type may comprise a fine neighbor discovery or a coarse neighbor discovery, wherein in the fine neighbor discovery, a neighbor list specifying known neighbors of the communication terminal is included in the message; and wherein in the coarse neighbor discovery, the neighbor list is not included in the message.

[0098] As used herein, the term "neighbor list" may refer to information that indicates any or all of other communication terminals that are neighbors with the communication terminal. "Known neighbors" refer to neighbors that have already been established, for example, in a previous neighbor discovery.

[0099] The neighbor list may comprise a set of one-hop or multiple-hops neighbor communications. HR-BSs and HR-RSs may also be included in the neighbor list.

[00100] In various embodiments, the message may be broadcast during a predetermined time slot. For example, the predetermined time slot may refer to the time domain resource of an OFDMA transmission slot. The predetermined time slot may be a scheduled time slot.

[00101] In various embodiments, in the coarse neighbor discovery, the message may be broadcast using a predetermined frequency. For example, the predetermined frequency may refer to the frequency domain resource of the OFDMA transmission slot.

[00102] In various embodiments, the indicator may comprise a node identifier, a Code Division Multiple Access (CDMA) ranging code and an Orthogonal Frequency-Division Multiple Access (OFDMA) transmission slot code for the predetermined time slot and the predetermined frequency.

[00103] In one embodiment, the message may comprise the Code Division Multiple Access (CDMA) ranging code of the indicator.

[00104] As used herein, the term "ranging code" generally refers to an identifier that is sent from a transmitter that can be used to determine the amount of transmission time that a signal takes to transfer from the transmitter to the receiver which can be used to determine the approximate distance between the transmitter and receiver. The term "ranging code" may be interchangably referred to as a ranging sequence.

[00105] An example illustrating neighbor discovery with respect to classification of the neighbor discovery type is provided. When there is a need for neighbor discovery, a HR-BS, for example, the base station 502 of Figure 5, classifies the need into coarse versus fine neighbor discovery.

[00106] For example, for coarse neighbor discovery,

o HR-BS/HR-RS sends an indicator or a control message to schedule one or multiple HR-MSs to broadcast ranging sequences in assigned channels. Multiple HR-MSs may share the same ranging sequence or the same assigned channel.

o Using the same or another indicator or control message, the serving HR- BS/HR-RS also schedules some other HR-MSs to listen on those channels scheduled for ranging sequences.

o Each HR-MS that is scheduled to receive ranging sequences shall determine what sequences it can correctly or properly decode, together with related information such as estimations of time/frequency offsets and signal strength.

o The receiving HR-MSs may report their measurements or findings to the serving HR-BS/HR-RS using a control message.

[00107] For coarse neighbor discovery, only one-hop neighborhood information is needed.

[00108] For example, for fine neighbor discovery,

o BS (or HR-BS) broadcasts a message informing a node to transmit a particular preamble over the full channel bandwidth at a specified future time (i.e., time slot),

o The scheduled node broadcasts the preamble, followed by information about its neighbors (e.g. neighbor list). All other nodes in the network tune in and try to receive,

o If a node can receive the preamble and neighbor information broadcast by the scheduled node, it concludes that it is a neighbor of the scheduled node, and also update the list of the scheduled node's neighbors.

[00109] For fine neighbor discovery, both one-hop and two-hop neighborhood information is required. In the data transmission following the preamble, a node may also broadcast control information (such as uplink initial ranging) for coverage extension.

[00110] For both coarse and fine neighbor discovery, apart from the affirmative/negative information about neighbor relationship, a receiving node may also extract information such as delay offset, power attenuation, frequency shift, etc. for the channel between itself and a broadcasting node.

[00111] The classification of neighbor discovery into coarse and fine neighbor discovery allows the BS (or HR-BS) to effectively tradeoff between neighbor information quality and the cost of neighbor discovery.

[00112] The BS (or HR-BS) may choose between coarse and fine neighbor discovery based on the state of information collected. For example, if the discovery process has just been started, most of the nodes would not have populated its neighbor list. In that case, coarse neighbor discovery is more suitable. On the other hand, if coarse discovery has been carried out for long enough, fine neighbor discovery may be scheduled to propagate two-hop information.

[00113] Alternatively, the BS (or HR-BS) may choose between coarse and fine neighbor discovery based on the data backlog. For example, if there is no delay in critical data queued, the BS (or HR-BS) may schedule fine neighbor discovery, which normally consumes more system resource.

[00114] In the current 802.16 specification, a MS is only allowed to transmit to and receive from a BS or RS. MS-to-MS direct communication is not allowed, including broadcast and multicast. This characteristic significantly limits the capability of the 802.16 system when a critical network component such as a BS or RS is damaged, or the link from a BS to the network infrastructure is disrupted or cut off. In fact, with the current system capability, in case of a BS failure, all the MSs under the coverage of the BS has to stop communication and wait for the BS to resume its function or for a new BS to appears.

[00115] According to various embodiments, the protocols for scheduling ranging code broadcasting/decoding in coarse neighbor discovery and for scheduling preamble/data broadcasting/decoding in fine neighbor discovery are novel, with respect to current OFDMA wireless broadband specification.

[00116] In various embodiments, the message of the communication terminal may be scheduled in an uplink subframe and/or a downlink subframe of a frame structure of the IEEE 802.16 communication standard.

[00117] An exemplary frame structure of the IEEE 802.16 communication standard is as shown in Figure 2.

[00118] The communication terminal may be a transmitter and the HR-BS may be a receiver, on an uplink (UL). Likewise, the communication terminal may be a receiver and the HR-BS may be a transmitter, on a downlink (DL).

[00119] In various embodiments, the uplink subframe and/or the downlink subframe, each may comprise a transition gap, and a data and control message.

[00120] In order to enhance communication reliability, the communication terminal in accordance to various embodiments may be used to discover neighboring and routing path to other communication terminals. The communication terminal in accordance to various embodiments may also forward data and control message for other communication terminals. It is therefore necessary to support communication terminal broadcasting considering the nature of neighbor and path discovery.

[00121] For coarse neighbor discovery, 802.16m is used as baseline Physical (PHY)/Media Access Control (MAC) specification for 802.16η.

[00122] As described above, coarse neighbor discovery may be based on communication terminals broadcasting CDMA ranging codes. In one example, the codes may be selected as a subset of the 256 ranging codes in 802.16m. In another example, new CDMA codes may be designed to improve operation efficiency. For example, shorter codes may be designed to shorten broadcasting/decoding time.

[00123] Figure 7(a) shows the scheduling of standard ranging operation in current 802.16m frame structure and Figure 7(b) shows network-discovery ranging being scheduled in a 802.16m frame structure.

[00124] In Figure 7(a), ranging operation may be performed in an uplink (UL) subframe 700 of a frame 702 in the 802.16m frame structure 704. A Transmit/Receive Transit Gap (TTG) 706 may be included for transmitting communication terminal change from receiving state to transmitting state. An UL data and control message 708 and a ranging code 710 may also be included.

[00125] With reference to Figure 7(b), in one example, the ranging-based discovery period may be scheduled in a downlink subframe 712. A DL data and control message 714, node (ND) ranging code 716 and an advanced-map (A-MAP) 718, which transmits a specific user control or the control and resource allocation information, may be included.

[00126] In another example, the ranging-based discovery period may be scheduled in an uplink subframe 720. A UL data and control message 722, normal ranging code 724 and ND ranging code 726 may be included.

[00127] In each of these examples, a TTG period 728, 730 may be included to allow the broadcasting (transmitting) communication terminal to switch from receiving state to transmitting state. [00128] In various embodiments, in the fine neighbor discovery, the message may comprise a preamble of a frame structure of the IEEE 802.16 communication standard. The term "preamble" is as defined above.

[00129] The message may be scheduled in a reserved subframe of the frame structure.

[00130] The reserved subframe may comprise a transition gap. For example, the transition gap may be TTG.

[00131] In various embodiments, in the fine neighbor discovery, the communication terminal may update its neighbor list with the at least one other communication terminal if it has been determined that the communication terminal is a neighbor of the at least one other communication terminal.

[00132] For fine neighbor discovery, 802.16m is used as baseline Physical (PHY)/Media Access Control (MAC) specification for 802.16η.

[00133] Enable the communication terminal (HR-MS) broadcasting means that one communication terminal (HR-MS) broadcasts some signal or information. A possible signal/information may be a preamble, a node identity, a neighbor list and/or path discovery information. All other communication terminals or nodes should listen to the media. With the current 802.16 frame structure, the HR-MS receives in a downlink subframe and transmits in an uplink subframe. However, neighbor discovery requires the communication terminals to transmit and receive at the same time. This indicates that the HR-MS neighbor and path discovery cannot be simply put on either the downlink or uplink sub-frames of the 802.16m.

[00134] With reference to the 802.16m, in one example as shown in Figure 8, one subframe 800 for HR-MS communication is reserved for neighbor and path discovery, and one subframe 800 in each superframe 802 is reserved for HR-MS broadcasting.

[00135] A 802.16m subframe, for example the subframe 800, usually comprises but not limited to about five - about nine symbols, for example, the OFDMA symbol 804. The number of symbols depends on the frame types, which is determined by the bandwidth. For a typical bandwidth such as 5 MHz, 10 MHz, and 20 MHz, the number of symbols in a sub-frame may be, for example, six. [00136] To enable a HR-MS to perform the neighbor discovery, a Transmit/Receive Transit Gap (TTG) 806 or a Receive/Transmit Transition Gap (RTG) may be necessary for the transmitting HR-MS change from receiving state to transmitting state or for HR- MSs in transmitting state change to receiving state. Therefore, one symbol time would be necessary to be reserved for TTG 806/RTG. For example, the TTG 806 or RTG each may have a duration of about 95 - about 160 μβ.

[00137] Following the TTG 806/RTG, a preamble 808 may be transmitted for the nearby HR-MSs discovering the transmitting HR-RS/HR-MS. Therefore, one symbol time is reserved for preamble transmitting. The BS should let all HR-RS/HR-MS know which HR-RS/HR-MS is transmitting in the specific subframe via control messages. Figure 8 shows an example of preamble transmitting.

[00138] As an example, for a similar scheme for 802.16j Mobile Multi-hop Relaying technology, the relay-amble is transmitted in the downlink relay zone.

[00139] Information that is to be included in neighbor and path discovery may be selected from the group consisting of the identifier of the node, the list of neighbor, the link quality, hop count information and any combination thereof. For the path discovery, the source and destination station ID, hop count, sequence number and other routing path related information is to be included in the information.

[00140] In the event that hierarchical preambles are used for synchronization, such as in 802.16m, the preamble used in neighbor discovery subframe is for fine synchronization. A coarse synchronization preamble may be priorly transmitted. For example, the place where a BS transmits coarse synchronization preamble is at the beginning of second frame within each superframe in 802.16m.

[00141] With the above scheme for 802.16m, the subframe used for neighbor discovery may be efficiently scheduled by reserving one or more subframes within each superframe for neighbor and path discovery. The above described method may be slow in path discovery when HR network supporting multi-hop relay since the neighbor discovery is a periodical event and path discovery sometimes is a burst event.

[00142] For example, to accelerate path discovery, a flexible framework as shown in Figure 9 is proposed to enable the neighbor and path discovery. First of all, since neighbor discovery is a periodic event, an HR-MS/RS may periodically transmit a beacon to disclose some basic topology information to the network. Therefore some subframes, for example, subframes 900, are allocated periodically for neighbor discovery. Second, path discovery is an on-demand transmission, therefore, some subframes, for example, subframes 902, are reserved for random access. Subframes 904 not specified in the reservation may still be used for normal downlink and uplink data transmission.

[00143] To integrate the above design into 802.16η amendment, a few parameters may be defined to describe the framework as shown in Table 1.

[00144] Table 1

[00145] The above parameters may be put in the superframe headers (SFH).

[00146] Control messages may have to be exchanged among the HR-RS and the HR- MS regarding the position of superframe, frame offset, subframe offset and slot number allocated for neighbor discovery in each contention window.

[00147] With preamble transmission, HR-RS/HR-MS can discover neighbors nearby. However, according to Figure 4, the HR-MS may also be expected to be able to help other HR-MSs in data and control message forwarding. In one example as shown in Figure 10, the HR-MS 1000 may help in range extension without changing its role to a HR-RS.

[00148] In order to support data and control message forwarding, the HR-MS 1000 may have to transmit more system information, not just the preamble for neighbor discovery. The information enables a HR-MS, for example, the HR-MS 1002, outside the coverage, where the coverage is as defined by an encircled area 1004, to indicate its need for communication.

[00149] Figure 11 shows an extended neighbor discovery subframe for HR-MS range extension.

[00150] Neighbor discovery may be extended by allowing the HR-MS, for example, the HR-MS 1000 of Figure 10, using one more symbol time for network access information transmitting. The HR-MS may either use the whole band or only use part thereof for transmission. If the whole band is used, then the HR-MS may tell HR-MS outside coverage, for example, the HR-MS 1002 of Figure 10, to send in a ranging code in some other locations of frames that follows. Alternatively, the frequency band resources may be divided into two parts: one part of frequency resources being used for system access information transmission while the other part may be reserved for the HR- MS outside the coverage transmitting ranging code. A HR-MS in transmission or transmitting state will not be able to receive the ranging code. However, a HR-MS in listening mode may receive the ranging code and forward the message to a HR-BS, for example, the HR-BS 1006 of Figure 10. The HR-MS may forward the ranging code. Since the HR-BS may receive the same ranging code from a few HR-MSs, the HR-BS may choose one of them and request it to forward control messages to the HR-MS who sends the ranging code.

[00151] Figure 11 shows the subframe for neighbor discovery and HR-MS range extension. In Figure 11, the neighbor discovery subframe 1100 may comprise TTGs, for example, the TTG 1102 and preambles, for example, the preamble 1104. The preamble may comprise a part 1106 for ranging codes, for example, the ranging code which is the HR-MS outside the coverage transmitting ranging code, and another part 1108 for system access information transmission as described above.

[00152] In a third aspect, a base station operable with a plurality of communication terminals of a cellular mobile communication system is provided as shown in Figure 12. In Figure 12, the base station 1200 comprises a determiner 1202 configured to determine a neighbor discovery type for performing neighbor discovery on the plurality of communication terminals; and an indicator generator 1204 configured to generate an indicator indicating the neighbor discovery to perform on the plurality of communication terminals depending on the determined neighbor discovery type.

[00153] The terms "base station", "communication terminal", "communication system", "neighbor discovery type", "neighbor discovery", and "indicator" are as defined above.

[00154] The base station 1200 may be the base station 502 of Figure 5. The base station may a HR-BS.

[00155] In a fourth aspect, a method of determining a neighbor for a communication terminal of a cellular mobile communication system is provided as shown in Figure 13. In Figure 13, the method 1300 comprises receiving an indicator from a base station indicating a neighbor discovery type 1302; broadcasting from the communication terminal a message based on the indicator 1304; and determining based on the neighbor discovery type whether at least one other communication terminal in the communication system is a neighbor of the communication terminal if the at least one other communication terminal receives the message 1306.

[00156] The terms "receive" or "receiving", "indicator", "communication system", "neighbor discovery type", "message", "base station", "communication terminal", "neighbor discovery", "broadcast" or "broadcasting", "neighbor" and "indicator" are as defined above.

[00157] The method 1300 is flexible to support both fine and coarse neighbor and path discovery schemes for 802.16η networks. When there is a need for neighbor or path discovery, the base station starts by scheduling one or multiple communication terminals, for example, mobile stations to broadcast some predetermined bit sequences. [00158] For fine neighbor/path discovery, the predetermined bit sequences may be 802.16 Orthogonal Frequency-Division Multiple Access (OFDMA) preambles. These preambles may also be followed by two-hop neighborhood information. The fine neighbor discovery may also support range-extension in 802.16η network.

[00159] In coarse neighbor discovery, the predetermined bit sequences may be 802.16 CDMA ranging codes. For coarse neighbor discovery, one-hop neighbor information may be embedded within the ranging codes so that no extra transmission is required.

[00160] Neighbor discovery may be an important procedure for alternative path management and coverage To further illustrate neighbor discovery, a further example with respect to 802.16e based HR-networks is provided.

[00161] Figure 14 shows an exemplary method for neighbor discovery in 802.16e based HR-networks. The detailed procedure is explained in the following steps:

1) For 802.16e based HR-networks, HR-BS may schedule the HR-MS to transmit preambles for neighbor discovery.

2) HR-MS should send a predetermined preamble at the schedule time slot.

3) All those HR-MS hear the preamble and knows the preamble is for neighbor discovery should report to the relative BS/RS of the findings. The findings may include the signal strength.

4) The preamble use by BS for downlink synchronization and the preamble used for neighbor discovery may be different.

5) BS may notify the schedule of transmission neighbor discovery preambles, the corresponding node identifier and other necessary information for neighbor discovery before the transmission happens.

6) A few HR-MS may be scheduled to transmit the neighbor discovery preambles at the same time. The preambles used by HR-MS may be the different when they transmit at the same time.

7) For the 802.16e based HR-Network, the BS may reserve one or two OFDM symbol time for neighbor discovery. 8) If two symbol durations are reserved for neighbor discovery, one symbol could be used for TTG so that those HR-MS in transmission state could turn from transmission state to receiving state.

9) If only one symbol is reserved, then the BS may require all those HR-MS not transmit should turn into receiving state before the specified HR-MSs transmit preambles for neighbor discovery.

[00162] In the context of various embodiments, the term "about" or "approximately" as applied to a numeric value encompasses the exact value and a variance of +/- 5% of the value.

[00163] The phrase "at least substantially" may include "exactly" and a variance of +/- 5% thereof. As an example and not limitation, the phrase "A is at least substantially the same as B" may encompass embodiments where A is exactly the same as B, or where A may be within a variance of +/- 5%, for example of a value, of B, or vice versa.

[00164] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

1. A communication terminal of a cellular mobile communication system, the communication terminal comprising:

a transceiver configured to broadcast a message indicating to at least one other communication terminal of the cellular mobile communication system that receives the message that the communication terminal is a neighbor of the at least one other communication terminal.

2; A communication terminal of a cellular mobile communication system, the communication terminal comprising:

a transceiver configured to receive a broadcast message from at least one other communication terminal of the cellular mobile communication system indicating that the communication terminal is a neighbor of the at least one other communication terminal.

3. The communication terminal as claimed in claim 1 or 2, wherein the communication system works in accordance with a IEEE 802.16 communication standard, or a Long Term Evolution (LTE) communication standard, or a LTE-advanced communication standard, or a OFDMA-based cellular communication standard.

4. The communication terminal as claimed in any one of claims 1 to 3, wherein the communication system comprises a communication network for providing a communication connection between the communication terminal and the at least one other communication terminal via at least one base station of the communication network.

5. The communication terminal as claimed in claim 4, wherein the message is broadcast without being communicated via the at least one base station of the communication network.

6. The communication terminal as claimed in claim 4 or 5, wherein the message is broadcast without the communication network being involved in the broadcast of the message.

7. The communication terminal as claimed in any one of claims 4 to 6, wherein the communication terminal receives from the at least one base station an indicator indicating that neighbor discovery is performed on the communication terminals depending on a neighbor discovery type determined by the at least one base station, and broadcasts the message accordingly.

8. The communication terminal as claimed in claim 7, wherein the neighbor discovery type comprises a fine neighbor discovery or a coarse neighbor discovery, wherein in the fine neighbor discovery, a neighbor list specifying known neighbors of the communication terminal is included in the message; and wherein in the coarse neighbor discovery, the neighbor list is not included in the message.

9. The communication terminal as claimed in claim 8, wherein the message is broadcast during a predetermined time slot.

10. The communication terminal as claimed in claim 9, wherein in the coarse neighbor discovery, the message is broadcast using a predetermined frequency.

11. The communication terminal as claimed in claim 10, wherein the indicator comprises a node identifier, a Code Division Multiple Access (CDMA) ranging code and an Orthogonal Frequency-Division Multiple Access (OFDMA) transmission slot code for the predetermined time slot and the predetermined frequency.

12. The communication terminal as claimed in claim 11, wherein the message comprises the Code Division Multiple Access (CDMA) ranging code of the indicator.

13. The communication terminal as claimed in any one of claims 10 to 12, wherein the message is scheduled in an uplink subframe and/or a downlink subframe of a frame structure of the IEEE 802.16 communication standard.

14. The commumcation terminal as claimed in claim 13, wherein the uplink subframe and/or the downlink subframe, each comprises a transition gap, and a data and control message.

15. The communication terminal as claimed in claim 9, wherein in the fine neighbor discovery, the message comprises a preamble of a frame structure of the IEEE 802.16 communication standard.

16. The communication terminal as claimed in claim 15, wherein the communication terminal updates its neighbor list with the at least one other communication terminal if it has been determined that the communication terminal is a neighbor of the at least one other communication terminal.

17. The communication terminal as claimed in claim 15 or 16, wherein the message is scheduled in a reserved subframe of the frame structure.

18. The communication terminal as claimed in claim 17, wherein the reserved subframe comprises a transition gap.

19. A base station operable with a plurality of communication terminals of a cellular mobile communication system, the base station comprising:

a determiner configured to determine a neighbor discovery type for performing neighbor discovery on the plurality of communication terminals; and an indicator generator configured to generate an indicator indicating the neighbor discovery to perform on the plurality of communication terminals depending on the determined neighbor discovery type.

20. A method of determining a neighbor for a communication terminal of a cellular mobile communication system, the method comprising:

receiving an indicator from a base station indicating a neighbor discovery type; broadcasting from the communication terminal a message based on the indicator; and

determining based on the neighbor discovery type whether at least one other communication terminal in the communication system is a neighbor of the communication terminal if the at least one other communication terminal receives the message.