WO2007107089A1

WO2007107089A1 - System for minimizing signaling overhead in ofdma-based communication systems

Info

Publication number: WO2007107089A1
Application number: PCT/CN2007/000846
Authority: WO
Inventors: Yunsong Yang; Anthony Soong; Jianmin Lu; Jung Woon Lee
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-03-17
Filing date: 2007-03-16
Publication date: 2007-09-27

Abstract

A system of physical layer packet format and signaling methods is disclosed, wherein signaling overhead is minimized in applications where multiple users share air interface resources; improving efficiency in orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA) communication systems.

Description

SYSTEM FOR MINIMIZING SIGNALING OVERHEAD IN OFDMA-BASED COMMUNICATION SYSTEMS

Field of the Technology

The present invention relates generally to wireless communications systems, and more particularly, to a versatile system for physical layer packet formatting and signaling that minimizes signaling overhead and improves efficiency in orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA) based communication systems.

Background of the Invention

In a wireless multiple access communication system, the wireless traffic channel resource, e.g., bandwidth and time interval, is shared by all the wireless terminals, i.e., mobile units, in a particular cell. Efficient allocation of this traffic channel resource is very important, as it directly impacts the utilization of the traffic channel resource and the quality of service perceived by individual wireless terminal users. One such wireless communications system is the Orthogonal Frequency Division Multiplexing (OFDM) based Multiple Access system.

OFDM represents a different system design approach. It can be considered a combination of modulation and multiple access schemes that segment a communications channel in such a way that many users can share it. Whereas TDMA segments according to time and CDMA segments according to spreading codes, OFDM segments according to frequency. It is a technique that divides the spectrum into a number of equally spaced tones, and carries a portion of a user's information on each tone. OFDM can be viewed as one form of frequency division multiplexing (FDM). However, OFDM has an important special property, in that each tone is orthogonal with every other tone. FDM typically requires frequency guard bands between the frequencies, so that they do not interfere with each other. OFDM allows the spectrum of each tone to overlap, and since they are orthogonal, they do not interfere with each other. By allowing the tones to overlap, the overall amount of spectrum occupied is reduced. OFDM can also be considered a multiple access technique, since an individual tone or groups of tones can be assigned to different users. Multiple users share a given bandwidth in this manner, yielding orthogonal frequency division multiple access, or OFDMA. Each user may be assigned a predetermined number of tones when they have information to send, or alternatively, a user can be assigned a variable number of tones based on the amount of information they have to send. Assignments are controlled by the media access control (MAC) layer, which schedules the resource assignments based on user demand.

In a wideband wireless communications system, signal may decrease from frequency selective fading, due to multi-path transmissions. Conventional OFDM systems have proposed overcoming frequency selective fading by dividing total bandwidth into a plurality of subcarriers, such that the bandwidth on each subcarrier is sufficiently narrow to enable the data modulation symbols carried by that subcarrier to experience relatively flat fading.

OFDMA systems commonly use an OFDM modulation technique to multiplex the data traffic of a plurality of mobile stations, in both frequency and time. In a cellular communication network based on OFDMA, a base station communicates with mobile stations that are within its coverage area by using signals that are orthogonal in frequency, thereby eliminating intra-cell interference.

For a multi-carrier (OFDM) system, the transmission resource is the frequency- time block. To support hybrid automatic request (HARQ) - and advanced retransmission strategy that allows for retransmissions directly at the physical/MAC layer, without involving higher layer mechanisms and inducing delay - the time line may be divided into several intervals, and the transmission of one packet may occupy only one interval. In addition, frequency allocation normally consists of a group of subcarriers.

Utilizing the concept of a channel tree, transmission granularity may be considered as a base node. Transmission granularity refers to the size of objects transmitted and received as a unit. For example, packet networks send and receive data in packets. Even if only some of the bits of a packet are erased or corrupted, the whole packet is discarded and mechanisms (e.g., forward error correction, request for resend) are activated to recover the packet as a whole.

Thus, such objects are either received error-free or are erased in their entirety. In some applications, an object's size could be the size of the transmission packets or could be smaller. In a channel tree, a parent node may have a set of child nodes. The relationships between the children and parent nodes do not overlap. It is understood that much larger resource allocation is possible with a higher layer tree node.

To reduce assignment signaling overhead, a system may use "synchronous HARQ" and provide support for "sticky" assignments. With synchronous HARQ, resources for successive retransmissions are not independently scheduled, but rather are retained for all re-transmissions associated with a packet. Thus, assignment of a set of hop-ports applies to an interval (or "interlace"). Assignments on different interlaces are independent, and an AT may be given resources on multiple interlaces.

Assignments can be sticky or non-sticky. Sticky assignments are useful to reduce assignment overhead required when it is beneficial to schedule multiple users simultaneously, and to eliminate request latency for RL transmissions. When an assignment is non-sticky, the assignment expires on successful packet decode, or when the packet fails to decode after the maximum number of H-ARQ retransmissions allowed for the packet. When assignments are sticky, the assignment persists as long as the assigned resource is in use. An assignment is in use as long as either a packet or an erasure sequence is transmitted using the assignment. The erasure sequence is simply a one-bit "keep alive" indication used to inform the receiver that the assignment should be retained even though a data packet might not be available for transmission using the assignment. If neither a packet nor an erasure sequence is transmitted using the assignment, the assignment expires and the resources are free for subsequent allocation. In addition, it is possible for the AP to send an explicit message that ends an assignment.

To reduce overhead required to specify sets of hop ports in a system, a finite space of channel IDs are defined that map to specific sets of hop ports, and are used to communicate assignments to ATs. Because assignments can be sticky, and to combat fragmentation of resources in the system due to the finite mapping of channel IDs, the system supports supplemental assignments that add sets of hop ports to the existing set allocated to an AT for an interlace. Such supplemental assignments are sent to augment an AT's allocation between packet transmissions.

The mapping between channel IDs and hop-ports is defined using the channel tree (as mentioned above), such as the one illustrated in FIG. 1. Each node on the tree is given a unique channel ID. For example, in FIG. 1, the channel tree shows that there are 32 base nodes in the system, namely

, wherein the superscript denotes a specific node layer and the subscript denotes a specific node ID. As a further example one can see that node Lf₅ consists of base node Lf_x and Lf₂ and thus can be used to transmit larger traffic. Further, each base node (nodes at the bottom of the tree) is mapped to a set of hop ports. A channel ID then maps to the set of hop ports mapped by the base nodes under the node of the channel ID.

Generally speaking, there are two kinds of resource assignments: sticky and non sticky. In order to make the communication between base stations and terminals more efficient, a concept of sticky assignments is illustrated. Sticky assignments are useful in a scheduled data transmission system in cases where many users are competing for limited assignment message resources. A sticky assignment is when a resource (e.g., a channel) that is assigned to a particular user continues to be available to that user after the standard unit of transmission (e.g., packet) is completed. Thus, a new assignment message is not necessary to enable that user to continue transmission.

When an assignment is sticky, the assignment persists as long as the assigned resource is in use. In terms of reducing signaling overhead, sticky assignments are useful for the long standing and non-bursty traffic, such as VoIP. However, it is likely that the resource assignment granularity is larger than one traffic loading. In this case, it is helpful to share the same resource with several users or traffics. When an assignment is non-sticky, the assignment expires on the end this packet transmission.

Thus, significant signaling overhead is present in OFDMA systems. Receiving terminals need to know which sub-carriers are assigned to them; and this affects the system's performance. Sub-carrier attenuations may be correlated over time, so few assignments change from one down-link phase to the next. Therefore, there is a need for structures and methods that allow multiple users to share air interface resources, including physical layer packet formats and signaling methods that optimize overall system performance.

Summary of the Invention

The present invention discloses novel methods and constructs whereby multiple users efficiently share air interface resources, by providing embodiments of physical layer packet format and signaling methods wherein multiple users may share air interface resources, thereby optimizing overall system efficiency.

The present invention also discloses a method and apparatus for a plurality of users to share the radio resources that are assigned to a particular user using the sticky assignments.

The present invention addresses one or more of the issues discussed above by providing methods and systems that can be advantageously utilized to allow multiple users to share resources. The present invention also finds utility in a wide variety of applications.

Specifically, the present invention discloses a novel method and apparatus wherein a plurality of users can share the radio resources that are assigned to a particular user using the sticky assignments.

An objective of this invention is to provide the packet structure to allow for the sharing by a plurality of users the radio resources which have already been assigned, with a sticky assignment, to a particular user.

Another objective of this invention is to provide the signaling necessary for the sharing by a plurality of users the radio resources which have already been assigned, with a sticky assignment, to a particular user. In so doing, the efficiency of the system is improved.

Therefore, in accordance with the previous summary, objects, features and advantages, the present disclosure will become more apparent to a person of the ordinary skill in the art from the following description and the appended claims when taken in conjunction with the accompanying drawings. The following description and drawings set forth in detail a number of illustrative embodiments of the invention. These embodiments are indicative of but a few of the various ways in which the present invention may be utilized.

Brief Description of the Drawings

For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

FIG. 1 depicts mapping between channel IDs and hop-ports using a channel tree structure;

FIG. 2 depicts a representative embodiment of a physical layer packet (PLP) of a multi-user packet (MUP) in a wireless system according to the present invention;

FIG. 3 depicts a representative embodiment of a traffic channel in wireless system utilizing the implementation of a New or Old sign, according to the present invention; and,

FIG. 4 graphically depicts a method for transmitting a multi-user packet wherein the header and payload parts of the multi-user packet (MUP) are separately encoded, modulated and multiplexed to the frequency resource, in accordance with the present invention.

FIG. 5 is a flow diagram depicting a method of enabling radio resource sharing in an OFDMA system according to the present invention; and

FIG. 6 illustrates an example of resource allocation for a data packet and a new Hybrid Automatic Request (H-ARQ) indicator according to the present invention.

Detailed Description of the Invention

The following discussion is presented to enable a person skilled in the art to make and use the invention. The general principles described herein may be applied to embodiments and applications other than those detailed below without departing from the spirit and scope of the present invention as defined herein. The present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

The present invention provides a unique method and system for minimizing signaling overhead by way of a multi-user packet (MUP) by sharing air interface resources for improvement of efficiency in OFDMA-based communication systems. For VoIP applications, voice frames have to be placed into IP packets. The added protocol overhead represents an intolerable amount of spectral inefficiency for wireless mobile networks. The present invention addresses the minimization of such overhead.

According to the present invention, the physical layer packet format and an associated signaling method are disclosed. With this method, multiple users can share the same air interface resource, resulting in improved and increased system efficiency.

In a wireless environment, an access network (AN) (not shown) assigns a group of access terminals (AT) (not shown) with a channel node comprising at least one or a plurality of base nodes. Specifically, the access network (AN) assigns a short ID with each user as an alternative to a standard long identifier, which is usually larger than 10 bits. It should be understood that such an assignment of a short ID may or may not happen in one frame. That is, in some situations the assignment of the short ID may be a dynamic assignment. One example would be wherein the access network AN assigns five (5) users with a specific channel node such as Zl₇ ⁶ , wherein Zl₇ ⁶ comprises base node Lf₁ , Z⁶^ , Lf₃ and Lf₄. In such an example each user would be associated with a 3 bit ID ranging from 0 to 4.

Further in accordance with the present invention, in each available frame, the access network (AN) will schedule at least one user, wherein the AN aggregates the payloads together into a physical layer packet (PLP). It should be understood from the present invention regarding acknowledgement feedback that the number of scheduled users will be equal to or less than the number of base nodes. Specifically, in above example, the access network (AN) can schedule up to four (4) users at any particular time. Furthermore, to ensure that multiple users encounter similar receiving quality, it is preferred by the present invention to put the users of similar channel quality together to form a physical layer packet (PLP). With reference now to FIG. 2, the present invention discloses an implementation of a physical layer packet (PLP) 10 format comprising a physical layer packet header 20 and a physical layer packet payload 30. In the preferred embodiment of the invention described, a multi-user packet (MUP) is separated into at least a physical layer packet header section 20 and a physical layer packet data or payload section 30. The physical layer packet header section 20 contains information that assists the mobile station with detection of the multi-user packet (MUP). Consequently, as will be described further below, the header sections 20 can comprise such information as the MAC ID of the users 50 being serves by a specific multi-user packet (MUP) and where in the multi-user packet (MUP) the data for each user that is sent is residing.

Moreover, the size of the header section 20 is always known to the mobile station as it is entirely determined by the resource allocation communicated to the mobile station. The present invention utilizes a separate cyclic redundancy check (CRC) algorithm that is appended to the physical layer packet header section 20 and the physical layer packet data or payload section 30. The header section 20 and the data or payload section 30 are then encoded separately. The encoded bits of the multi-user packet (MUP) are then separated into sub-packets. The first sub-packet always contains the entire header section 20 and some or all of the encoded bits from the data or payload section 30. The location of the header section 20 in the first sub-packet is also known to the mobile station. For example, the header section 20 can always occupy the beginning of the sub-packet.

Given this, the mobile station always attempts to detect the header section 20 information. The mobile station is intelligent to know that the header section 20 is decoded correctly if the header CRC passes. If the mobile station detects the header section 20, then the mobile station knows that this is the first sub-packet of a new MUP. If the mobile station does not detect the header section 20, then the mobile station knows that this sub-packet is the continuation of an existing multi-user packet (MUP).

With continued reference to FIG. 2, the physical layer packet header 20 of the physical layer packet (PLP) 10 comprises the fields for the number of users 40 which denotes the number of user in a specific physical layer packet (PLP) 10. By way of example, if the maximum user number is 4, the number of users field 40 requires 2 bits.

In addition, the present invention's physical layer packet header 20 further comprises user header data, comprising a user ID 50 and the length 60 (i.e., the payload length) of the associated user ID's MAC packet 90 for the associated user ID 50. In sequenced repetition, additional user ID fields for further subsequent MAC packets and associated lengths of the subsequent MAC packet fields will repeat for the times of the number of users comprising the physical layer packet 10. The repeated/additional packet user IDs and length assignments are indicated in FIG. 2 by the ellipses 65 (i.e.,...). The user ID 50 and the length 60 of the MAC packet 90 have the fix length, for example, 2 bits for user ID and 10 bits for payload length. In addition, the physical layer packet header 20 further comprises the user ID 70 of the last MAC packet 100 and the length 80 of the last MAC packet 100 (i.e., the payload).

FIG. 2 further illustrates the physical layer packet payload (PLP) 30. The physical layer packet payload (PLP) 30, the payload of the first MAC packet 90 and the payload of the last MAC packet 100 are depicted. As mentioned above, such arrangement enables the position of each user's payload (e.g., 90...100) to be identified to the receiver to enable specific payload ownership determination. The payloads (e.g., 90...100) are sequentially placed in the same order as occurs in the physical layer packet header 20. It will be understood to one skilled in the art that in sequenced repetition, additional MAC packet lengths (i.e., the payload) will repeat for the times of the number of users comprised in the physical layer packet header 20 comprising the physical layer packet 10. The repeated/additional additional MAC packet lengths assignments are indicated in FIG. 2 by the ellipses 95 (i.e.,...). In addition, if the total length of the physical layer packet 10 is less than that required by the physical layer packet 10 (PLP), padding 110 may be inserted in the tail of the physical layer packet payload 30. It should be recognized by one skilled in the art that the positions of the described fields can be interexchanged without departing from the scope and spirit of the present invention.

By way of example, according to that just described above, if an access network (AN) schedules user IDs of 2, 0 and 4 together and the payload lengths of the user IDs are 70, 150 and 250 bits respectively, and the physical layer packet (PLP) 10 size is 520 bits, the fields will be filled as depicted below:

a) number of users: 3;

b) 1st user ID: 2;

c) 1st payload length: 70;

d) 2nd user ID: 0;

e) 2nd payload length: 150;

f) 3rd user ID: 4;

g) 3rd payload length: 250;

h) 1st payload: user ID 2's data;

i) 2nd payload: user ID O's data;

j) 3rd payload: user ID 4's data; and

k) padding: to fill the remaining vacant fields to form the completed 520- bit multiple user packet (MUP). For example, a 50-bit padding would be required in the present example to complete the 520-bit MUP.

Furthermore, and by way of further example, the present invention provides for alternative formats for the physical layer packet (PLP) to facilitate functionality similar to the embodiment described above. Specifically, one such alternative comprises a fixed number of user headers, thereby eliminating the number of users field 40 as described in association with FIG. 2 above. In the event that the number of users 40 is less than the number of user headers, the left field of the physical layer packet header 20 can be marked as reflecting "empty."

When traffic information is transmitted from a base station to a mobile station, the base station waits to receive a confirmation message from the mobile station indicating whether the mobile station has received the transmitted information without errors. If the mobile station receives the information correctly, it transmits an ACKnowledge (ACK) confirmation message. If the mobile station receives the information with errors or with an unacceptable amount of errors, it transmits back a Negative ACKnowledgement (NACK) message to the base station informing the base station that the information was received with errors. The base station retransmits the traffic information upon reception of a NACK confirmation message.

According to the present invention, when a potential user(s) has successfully decoded the physical layer packet (PLP) 10, the packet receiver transmits an ACK message to the sender over a reverse link channel called the Reverse ACKnowledgement Channel (RACKCH).

According to the present invention the modulation scheme used on the reverse ACKnowledgement channel is on-off keying (OOK). Typically, a RACKCH ID is associated with a forward link base node. For example, a RACKCH ID of 1 is associated with FL base node 41 (refer to FIG. 1 for reference to Lf ), a RACKCH ID of 2 is associated with FL base node Lf₂ (refer to FIG. 1 for reference to Lf₂), etc., until a RACKCH ID of 32 is associated with FL base node Lf₂ (refer to FIG. 1 for reference to Lf₂). Because the multi-user packet (MUP) occupies the channel node the RACKCH IDs related are 1, 2, 3, and 4.

Furthermore, if there are multiple user data in the physical layer packet (PLP) 10, the RACKCH ID is associated with the particular user through one to one mapping. Such mapping can be established by various methods. By way of a non-limiting example, the mapping is established by the sequence of the user existing in the physical layer packet (PLP) 10. In the above example, a user ID of 2 is the first user ID in the PLP. Therefore, it will respond to the ACK through the RACKCH ID of 1. Similarly, a user ID of 0 is the second user ID in the PLP, so it is associated with the RACKCH ID of 2. In like manner, a user ID of 4 is the third user ID in the PLP, so it is associated with a RACKCH ID of 3. In situations where only one user exists in the PLP, the access terminal (AT) will always use the lowest indexed RACKCH associated with the assigned Node ID to transmit the necessary feedback.

If the access network (AN) did not receive in entirety the acknowledgement from the user IDs included in the PLP and the maximum retransmission times is not reached, the access network (AN) will retransmit the PLP in the next interlace. Otherwise, the access network (AN) will schedule a new PLP in the next interlace.

The retransmission of the PLP described above can be a simply repeat of the prior PLP and in such a case, it is likely for the access terminal (AT) receiving the duplicated packet. It should be understood by one skilled in the art that the duplication detection can be done in a higher layer.

In an alternative method according to the present invention, the access terminal (AN) transmits the PLP for a fixed number of interlaces. In such a situation the access terminal (AN) does not need the acknowledgement from the access terminal (AT). In this alternative method, the access network (AN) will notify the timeline when a new PLP begins by signaling to each potential access terminal (AT).

It yet another alternative method, the access network (AN) signals each potential user with the time when the new PLP begins. If the packet is not new and has not been decoded successfully, the potential user will try to decode it with the stored information of the prior interlaces since the last new PLP.

According to another embodiment of the present invention, it is often desirable to indicate to a mobile station when a new multi-user packet (MUP) is being transmitted from the base station to the mobile station. In one embodiment, the base station indicates to the mobile station that the base station is actively sending a new multiuser packet (MUP) to the mobile station. As previously stated, the multi-user packet (MUP) is sent to the mobile station in a plurality of sub-packets.

With reference to FIG. 4 what is graphically shown is that the header and payload parts of the multi-user packet (MUP) are separately encoded, modulated and multiplexed to its frequency resource according to the present invention.

Now with reference to FIG. 3, what is depicted is yet another implementation wherein the access network (AN) signals each potential user with the time when the new PLP begins by placing a New sign 200 or an Old sign 210 in the traffic channel. As FIG. 3 depicts, at the first subcarrier of the first symbol of each traffic frame 230, a New sign 200 or an Old sign 210 is binary phase shift keying (BPSK) modulated, such that "+1" reflects the new data packet and a "-1" reflects the retransmitted data packet. The New sign 200 or the Old sign 210 is transmitted with a target performance at 0.1% bit error rate (BER). If a sign can not achieve the desired accuracy, a plurality of modulated symbols can be placed to reach the desired 0.1% BER accuracy. For example, FIG. 3 depicts that there is another sign at the last subcarrier of the first symbol.

Another embodiment and implementation wherein the access network (AN) signals each potential user with the time when the new PLP begins by the access network (AN) is disclosed. Specifically, the access network (AN) places a New sign or an Old sign in the FL control channel in every frame. Each potential user listens to the FL control channel in the frame to determine if it is a New sign or an Old sign. If the sign denoting it is a new packet (i.e., New sign), the access terminal (AT) subsequently initiates a new decoding procedure. Otherwise, the access terminal (AT) regards that specific frame as retransmission and will try to decode it by a type of incremental redundancy scheme or chase combining scheme. The position of the New sign or Old sign in the FL control channel is notified to each potential user when a call is established.

Further, according to the present invention, it will be understood by one skilled in the art that this method can also be applied for a single user ID packet. If it is mandatory that only one user ID exist in the physical layer packet (PLP) 10 (See FIG. 2), then the access terminal (AT) addressing scheme is provided selective alternatives. For example, one alternative is that the access network (AN) assigns a particular scrambling code to each user ID. At a frame, the access network (AN) schedules a user ID and scrambles the PLP with its particular code. Therefore, only the target access terminal (AT) is able to decode and acknowledge as described above. In this case, there is no need for the user ID field 50 (See FIG. 2) in the PLP 10 format.

In yet another embodiment of the invention, an indicator, called the new multiuser packet (MUP) indicator, is always sent with every sub-packet to inform the mobile station if this is a continuation of the existing MUP or a new MUP. In order to simplify the detection hardware in the mobile station, the location of this indicator in the frame that carriers the sub-packet remains fixed. In this way, the mobile stations begin the detection of the sub-packet by first detecting the new MUP indicator to determine if this sub-packet is a continuation of an existing MUP or a new MUP. OFDMA is a system in which a plurality of users performs multiple access using OFDM. In a conventional OFDMA data transmission apparatus, a method is proposed to carry out both frequency division and time division when multiple access is performed. Also, to improve the error correction capability, diversity is carried out in a frequency direction and in a time direction.

A resource allocation from the base station may be valid for the transmission of one packet or for the transmission of multiple packets. If the resource is allocated for more than one packet of transmission, it is termed, a sticky assignment. If the resource is allocated for just one packet of transmission, it is termed, a non-sticky assignment. Those skilled in the art, would also know that significant savings in the overhead is possible with the sticky assignment.

However, with the sticky assignment, there exists a possibility of unused resources. This can occur, for a variety of reasons. For example, the sticky user may be a voice over internet protocol (VoIP) user and the VoIP packet early terminates or the 1/8 rate frames are blank off. When this occurs, resources that are already assigned to this user with the sticky assignment are left unused as the user waits for the arrival of the next VoIP packet.

The present invention provides unique methods to support sharing of radio resources in an OFDMA-based communication system. It is understood, however, that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components, signals, messages, protocols, and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the invention from that described in the claims. Well known elements are presented without detailed description in order not to obscure the present invention in unnecessary detail. For the most part, details unnecessary to obtain a complete understanding of the present invention have been omitted inasmuch as such details are within the skills of persons of ordinary skill in the relevant art. Details regarding control circuitry described herein are omitted, as such control circuits are within the skills of persons of ordinary skill in the relevant art. According to the present invention, the physical layer packet format and an associated signaling method are disclosed. Multiple users can share the same air interface resource thereby resulting in improved and increased efficiency. This packet format and associated signaling protocol is termed as the sharing format in this disclosure of the present invention.

According to the present invention, a packet structure is described to allow a user to determine if this packet is intended for the user. Consequently, in accordance with one aspect of the present invention, each user is assigned a unique scrambling code. In one embodiment, each sub-packet is assigned to a user and is separated into a header section and a data section. In another embodiment, each sub-packet is not separated into a header section and a data section.

A transmitter scrambles the data section of each sub-packet with a scrambling code of the user for which this sub-packet is intended for. In addition, a person of the ordinary skill in the art will understand that other methods, such as sending an explicit user ID in the header, are possible to signal the intended user for this sub-packet.

In accordance to another aspect of the present invention, a receiver of a user unscrambles the data portion of the sub-packet with the unique scrambling code that was assigned to the receiver of the user. If the sub-packet is for an intended user, the unscrambling process reverses the scrambling process performed at the transmitter and the receiver is able to detect if the receiver receives the sub-packet when a cyclic redundancy check (CRC) is performed. If, on the other hand, the receiver is not the intended user, the unscrambling process does not reverse the scrambling process at the receiver and the receiver is not able to detect the data. Consequently, the CRC will not check.

In accordance to another aspect of the invention, a method of implementing an H-ARQ is described to prevent the corruption of a detection buffer at a receiver. With an H-ARQ, the receiver will add the received information to a detection buffer at the receiver even when a CRC does not check. This is because with the H-ARQ, more than one transmission of the packet may be needed before sufficient energy is accumulated for the packet to be detected. Consequently, the receiver will add the information to the detection buffer even if the CRC does not check so that this information can be combined with the information obtained from the transmission of the next sub-packet. A corruption of the detection buffer, that is, a severe impairment to the detection performance, can happen if information intended for a user is mixed with information that is intended for another user. To avoid this corruption, a transmission protocol in a particular H-ARQ interlace is designed so that at a receiver an H-ARQ sequence is completed before another sequence is started. Furthermore, the beginning of a new H-ARQ sequence is signaled. If the receiver receives notification that a new H-ARQ sequence has started, the receiver flushes a detection buffer at the receiver. One embodiment of this signaling is to explicitly signal the beginning of the H-ARQ sequence in the header section of the sub-packet. A person of the ordinary skill in the art will understand, other methods, such as signaling the beginning of the H-ARQ sequence in a separate signaling channel, can be used for signaling the beginning of a new H-ARQ sequence.

In accordance to yet another aspect of the invention, a signaling protocol is designed to minimize the impact of a detection error of a new H-ARQ sequence indicator. In one embodiment, the beginning of a new H-ARQ sequence is indicated by a signal that toggles between two indicators when the transmission for a new H- ARQ sequence starts and the signal remains the same when the transmission is for the subsequent sub-packet of a previously failed sub-packet. Specifically, a transmitter transmits the same indicator with each sub-packet of the same H-ARQ sequence. With the beginning of a new H-ARQ sequence, the transmitter switches the indicator to the other indicator. In this embodiment, if a receiver misses transmission, the receiver can still detect the new H-ARQ indicator because the indicator in the subsequent sub- packet transmission is different from the indicator used in the previous packet transmission. Therefore, the new H-ARQ indicator used in this embodiment is efficiently robust to detection error.

FIG. 5 is a flow diagram depicting a method of enabling radio resource sharing in an OFDMA system according to the present invention. In this embodiment shown in FIG. 5, a process starts at step 101 and at step 103 a receiver waits for a new sub- packet to arrive. When the receiver receives the new sub-packet at step 103, then goes to step 105 determining whether a new H-ARQ sequence indicator is received. If no new H-ARQ sequence indicator is received, then goes to step 109; if a new H-ARQ sequence is received, then the process goes to step 107, where the new H-ARQ sequence is flushed to a H-ARQ buffer at the receiver. At step 109 received data is detected, and goes to step 111 determining whether a CRC is checked. If no CRC is checked, then goes to step 115, where the information of the received sub-packet is added to the H-ARQ buffer, then goes to step 117 where a non-receiving signal is sent, and the process continues at starting step 101. If step 111 determines that a CRC is checked, then goes to step 113 where an acknowledgment signal is sent, then the process continues at starting step 101.

In accordance to another aspect of the invention, the new H-ARQ indicator is transmitted to ensure its detection. In one embodiment, the second row of a fourth order Walsh matrix, i.e. Wj⁴ or "0101", is used for one indicator while the fourth row, i.e. W₃ ⁴ or "0110", is used for the other indicator. It should now be clear to those skilled in the art that since only 2 Walsh codes are used, the other two Walsh code may be used to multiplex other information such as, for example, transmit ID in a CDM fashion. ^'

Figure 6 shows an example of a resource assignment. In this example, eight distributed sub-carriers (201, 202, 203, 204, 205, 206, 207, and 208) are assigned. Four sub-carriers (202, 204, 206, and 208) are used to transmit the new H-ARQ indicator and the other four sub-carriers (201, 203, 205, and 207) are used for data transmission. This particular example also shows that the header part of the sub- packet consists of just the new H-ARQ indicator. Moreover, the four bits of this encoded indicator (header) are distributed within the assigned resource in order to take advantage of frequency diversity. The modulation format of the new H-ARQ indicator is also independent of the resource assignment and is Binary Phase Shift Keying (BPSK) modulated in this embodiment. It should now be clear to those skilled in the art that although one embodiment uses frequency distributed transmission, the transmission of the new H-ARQ indicator can be done using a number of different sub-carrier assignments. For example, the sub-carriers can be contiguous.

In yet another aspect of this invention, the power used to transmit the new H- ARQ indicator (header part of the sub-packet) may be different than that for the data part of the sub packet. In this embodiment, the system can ensure the reliability of the new H-ARQ indicator by transmitting the header with higher power. In yet another aspect of this invention, the usage of this sharing format is signaled. In one embodiment, the usage of this format is implied by the sticky assignment. That is, all transmission in response to the sticky assignment uses the sharing format. This means that all users that share the radio resource are assigned with a sticky assignment. In another embodiment, the usage of the sharing format is explicitly signaled in the assignment message. In this embodiment, the other users that share the resources that have been assigned to a user with a sticky assignment may or may not be assigned with a sticky assignment. It should now be clear to those skilled in the art that a variety of methods may be used to signal the usage of the sharing format.

In another aspect of the present invention, more than one encoder packet size and modulation and coding scheme (MCS) for the data segment may be associated with a particular resource assignment. In one embodiment, the modulation for the resource assignment is fixed and is explicitly signaled in the resource assignment. In addition, the encoder packet size may be different. Rate matching by either puncturing or repetition is used to match the rate to the resources assigned for the different encoder packet sizes. The number of different encoder packet sizes that are associated with a particular assignment is small and the receiver can blind detect among them. For example with a VoIP user where the vocoder can send full rate, Vi rate, ¹A rate and 1/8 rate frames, the repetition is used with the lower rate frames in order to make all frames of full rate. The receiver then blindly detects among the different rates. In another embodiment, the encoder packet size is explicitly signaled to the receiver in the header section.

In yet another aspect of the invention, the ACK and NACK responses for the H- ARQ process are sent with on off keying with the NACK being represented by the off (no transmission) and the ACK being represented by the ON. In this way, the processing at the receiver are the same for all users. For the users in which the data was not intended for it, this user will always sent a NACK. Consequently a plurality of unintended users can send the NACK with the same resource and have no information collide since all these users are using no transmission to signal the NACK. The intended user can also use the same resource to send the ACK without information collision because the intended user is the only user that will have a radio transmission (On). It should be clear to those of ordinary skill in the art that this method of signaling the ACK and NACK will save resources but other methods of transmitting the ACK and NACK responses are possible.

The previous description of the disclosed embodiments is provided to enable those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art and generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A communication system comprising: an access network; a plurality of access terminals, wherein the access network assigns the plurality of access terminals with a channel node, wherein the channel node comprises at least one base node; and wherein the access network assigns a short ID with at least one user, wherein the short ID assignment is dynamic.

2. The system of claim 1, wherein the access network schedules at least one user and the user's payload into a physical layer packet.

3. The system of claim 2, wherein the number of scheduled users is equal to or less than the number of base nodes.

4. The system of claim 3, wherein the traffic data for the users of similar channel quality form the physical layer packet.

5. The system of claim 1 wherein the short ID may be transferred over one or more frames.

6. A method of allocating transmission resources in a wireless communications system, comprising the steps of: providing physical layer packet format data; providing the physical layer packet format data to a communication station via a traffic channel; providing an access network; providing a plurality of access terminals; utilizing the access network to assign the plurality of access terminals a channel node; associating a user terminal with a channel node; and utilizing the access network to assign a short ID to the user, wherein the assignment is dynamic.

7. The method of claim 6 wherein the step of utilizing the access network to assign a annel node further comprises assigning a channel node that comprises at least one base de.

8. The method of claim 6 wherein the step of utilizing the access network to assign a ort ID further comprises assigning a short ID that may be transferred over one or more imes.

9. The method of claim 7, further comprising the step of utilizing the access network to hedule at least one user, and the user's payload, into a physical layer packet.

10. The method of claim 9, wherein the number of scheduled users is equal to or less an the number of base nodes.

11. The method of claim 10, wherein the traffic data for the users of similar channel iality form the physical layer packet.

12. A wireless communications system, in which physical layer packet format data is immunicated with an access terminal in association with a traffic channel, and in which air terface resources are shared amongst users in the communication system, the system >mprising: an access network; a plurality of access terminals communicatively associated with the access network; wherein the access network is adapted to assign the plurality of access terminals a iannel node; and wherein the access network is adapted to associate a short ID with at least one user.

13. The system of claim 12 wherein the channel node comprises at least one base node.

14. The system of claim 12 wherein the short ID may be transferred over one or more ames.

15. The system of claim 13, wherein the access network is adapted to schedule a user id the user's payload into a physical layer packet.

16. The system of claim 15, wherein the number of scheduled users is equal to or less ian the number of base nodes.

17. The system of claim 16, wherein the traffic data for the users of similar channel iality form the physical layer packet.

18. A method of enabling radio resource sharing in an OFDMA communication ^rstem, comprising: providing at least a packet; defining a plurality of sub-packets for the packet; assigning a unique scrambling code to each of the plurality of sub-packets; providing at least a receiver; designating the unique scrambling code to the receiver; providing at least a transmitter; performing a scrambling process on each of the plurality of sub-packets with the unique rambling code at the transmitter; performing a unscrambling process at the receiver on each of the plurality of sub- ackets with the unique scrambling code; reversing the scrambling process at the transmitter; and determining whether to the cyclic redundancy check (CRC) iecks at the receiver.

19. The method in claim 18, further comprising sending an acknowledgment from the ϊceiver of receiving one of the plurality of sub-packets with the unique scrambling code if ie receiver determines that the CRC checks.

20. The method in claim 18, further comprising sending a signal from the receiver of not ϊceiving one of the plurality of sub-packets with the unique scrambling code if the receiver etermines that the CRC does not check.

21. The method in claim 18, wherein each of the plurality of sub-packets is divided into data section and a header section.

22. The method in claim 21, further comprising: designating the unique scrambling code to the receiver; providing at least a transmitter; performing a scrambling process on the data section of each of the plurality of sub- ackets with the unique scrambling code at the transmitter; performing a unscrambling process at the receiver on the data part of each of the urality of sub-packets with the unique scrambling code; and reversing the scrambling process at the transmitter.

23. A method of enabling radio resource sharing in an OFDMA communication 'stem, comprising: providing at least a packet; defining a plurality of sub-packets for the packet; assigning a unique scrambling code to each of the plurality of sub-packets; providing at least a receiver; designating the unique scrambling code to the receiver; implementing a plurality of unique hybrid automatic request (H-ARQ) sequences; designating each of the plurality unique H-ARQ sequence to each of the plurality of sub- ickets; providing at least a transmitter; performing a scrambling process at the transmitter on each of the plurality of sub- ackets with the unique scrambling code; performing a unscrambling process at the receiver on each of the plurality of sub- ackets with the unique scrambling code; receiving a notification of a beginning of one of the plurality of unique H-ARQ jquence at the receiver; providing a detection buffer at the receiver; flushing the H-ARQ sequence to the detection buffer at the receiver; reversing the scrambling process at the transmitter; and determining whether to perform a cyclic redundancy check (CRC) at the receiver.

24. The method in claim 23, further comprising sending an acknowledgment from the jceiver of receiving one of the plurality of sub-packets with the unique scrambling code if ie receiver performs a CRC.

25. The method in claim 23, further comprising sending a signal from the receiver of not xeiving one of the plurality of sub-packets with the unique scrambling code if the receiver oes not perform a CRC.

26. The method in claim 23, further comprising providing a plurality of indicators ierein each of the plurality of indicators corresponds to a beginning of the plurality of dque H-ARQ sequences.