HK1164026A - Resource assignment in an enhanced uplink mobile communication system - Google Patents

Abstract

An apparatus, such as a base station, transmitting signalling information in a cellular communication system whereby a plurality of shared uplink transmission resources is divided into sets of mutually exclusive transmission resources. The apparatus comprises means for granting uplink resources to a wireless subscriber communication unit via a grant message for uplink transmission; means for receiving an uplink transmission from a wireless subscriber communication unit; means for deriving an uplink code resource identifier from the uplink transmission or the grant message; means for assigning at least one downlink code sequence used to carry downlink signalling information associated with the uplink transmission and which is derived using the uplink code resource identifier; and means for transmitting a downlink transmission comprising the at least one downlink code sequence to the wireless subscriber communication unit.

Description

Resource allocation in an enhanced uplink mobile communication system

The present application is a divisional application of the invention patent application having an application number of 200680030745.6, a filing date of 2006, 7/7, and a title of "resource allocation in an enhanced uplink mobile communication system".

Technical Field

The present invention relates to signalling within a cellular communication system, and in particular, but not exclusively, to signalling of acknowledgement signals within a third generation partnership project (3GPP) cellular communication system.

Background

Currently, third generation cellular communication systems are being initiated to further enhance the communication services provided to mobile users. The most widely deployed third generation communication systems are based on Code Division Multiple Access (CDMA) and Frequency Division Duplex (FDD) or Time Division Duplex (TDD) technologies. In a CDMA system, user separation is achieved by allocating different spreading and/or scrambling codes to different users on the same carrier frequency and within the same time interval. In Time Division Multiple Access (TDMA) systems, user separation is achieved by allocating different time slots to different users. In addition to TDMA, TDD provides for the use of the same carrier frequency for both uplink and downlink transmissions. An example of a communication system using this principle is the Universal Mobile Telecommunications System (UMTS). Further description of the Wideband CDMA (WCDMA) mode of CDMA, specifically UMTS, can be found in "WCDMAfor UMTS", Harri Holma (eds.), Antti Toskala (eds.), Wiley & Sons, 2001, ISBN 0471486876.

To provide enhanced communication services, third generation cellular communication systems are designed to support a variety of different services, including packet-based data communications. Similarly, existing second generation cellular communication systems, such as the global system for mobile communications (GSM) have been enhanced to support an increased number of different services. One such enhancement is the General Packet Radio System (GPRS), which is a system developed to support packet data based communications within a GSM communication system. Packet data communication is particularly suited for data services, which have dynamically changing communication requirements, such as internet access services.

For cellular mobile communication systems where traffic and services have non-constant data rates, it is efficient to dynamically share radio resources between users according to their needs at a particular time instant. This is in contrast to services with constant data rates, where radio resources appropriate to the serving data rate can be allocated on a long-term basis, e.g., for the duration of a call.

In the current UMTS TDD standard, uplink shared radio resources may be dynamically allocated (scheduled) by a scheduler in the Radio Network Controller (RNC). However, in order to operate efficiently, the scheduler needs to know the amount of uplink data waiting for uplink transmission on a single mobile user. This allows the scheduler to allocate resources to the users that need it most. In particular, it prevents wasting resources because resources are allocated to a mobile station that does not have any data to transmit.

Recently, a lot of efforts have been made to improve the uplink performance of especially 3GPP systems. One way of this improvement is to move the scheduling entity out of the RNC and into the radio base station to communicate with the wireless subscriber communication unit, so that transmission and retransmission delays can be reduced. Thus, faster and more efficient scheduling can be achieved. This further improves the perceived throughput of the end user. In such an embodiment, a scheduler located within the base station (rather than the RNC) is responsible for controlling the grant of uplink resources. Fast scheduling response to user traffic demands and channel conditions is desirable in improving scheduling efficiency and transmission delay for individual wireless user communication units.

In particular, in order to enable efficient communication of data bits over the air interface, retransmission of incorrectly received data packets has been specified for most 3GPP packet data services. In these systems, data retransmission is common. So-called hybrid schemes may also be used, in which the retransmitted corresponding signal is collected with the previously transmitted signal of the same data in the receiver prior to decoding, thereby iteratively improving the probability of correct decoding of the data. A hybrid and fast retransmission scheme is typically used because the best link efficiency (in terms of energy required for retransmission after each error-free transmitted bit) is achieved when the error probability of the first transmission is high (e.g., 10% to 50%). However, the air interface transmission delay associated with retransmission is very high because it includes acknowledgement feedback processing (e.g., delay waiting for possible acknowledgements before determining retransmission) and delay of retransmission data packet scheduling.

With respect to uplink multiple access, both FDD and TDD physical layers use spreading (using one or more sets of so-called channelization codes) after chip scrambling operations. For FDD uplink, each user is assigned a user-specific sequence for scrambling operations that, in conjunction with channelization code spreading, support separation of the respective user signals at the base station receiver. Conversely, for TDD, all users within a given cell use the same scrambling code. Users using the same time slot in TDD can thus be separated, mainly with having different physical channelization codes.

The result of this difference in uplink scrambling code allocation between FDD and TDD modes is that a limited set of channelization code resources must be allocated between competing users belonging to the same TDD cell, whereas in FDD, users in the same cell can use the same channelization code subject to some restrictions on the number of codes used and their spreading factors.

Within the enhanced uplink system environment within 3GPP, scheduling of uplink transmissions for users is performed by a base station. A low latency retransmission scheme is supported in which a base station sends a fast acknowledgement indicator back to a wireless subscriber communication unit associated with a particular block of transmission bits. If the transmission of the data block is received in error, the indicator is set to "NACK" (negative acknowledgement) by the base station, and upon receipt of the transmitted indicator, the wireless subscriber communication unit knows that the data is to be retransmitted. If the transmission of the data block is received without error, the indicator is set to "ACK" (acknowledged) by the base station, and upon its receipt, the wireless subscriber communication unit knows that the transmitted data has been correctly received and can select new data for transmission within any subsequent scheduling grant by the base station.

The channel used for transmitting ACK/NACK from the base station to the wireless subscriber communication unit is called E-HICH (enhanced uplink hybrid ARQ indicator channel). This channel must be a low data rate channel because it carries only one bit of information for each user that is active at the time. For FDD enhanced uplink, if the wireless user communication unit is inactive at a particular time, no acknowledgement need be sent and thus no acknowledgement is sent (the wireless user communication unit also does not expect to receive an acknowledgement).

For FDD, the acknowledgement indicator is encoded on the E-HICH channel by assigning a user-specific sequence of length "40" to each user using the enhanced uplink service in the cell. Notably, the sequence is allocated for the duration of an enhanced uplink "call". During silent periods between bursts of uplink transmissions, this code remains assigned to a particular user and cannot be reused by other users. This effectively limits the size of the possible active user population to 40 per E-HICH. Each E-HICH for FDD uses channelization coding with a spreading factor of 128, thus consuming 1/128 of the available downlink coding resources (note: scrambling coding is cell-specific in the downlink direction for FDD, unlike the uplink). If the number of people or users exceeds 40, then additional E-HICHs must be configured, consuming another 1/128 of the available downlink coding resources, and so on.

Another problem associated with the efficient use of valuable resources has been the recent desire for "always-on" internet connectivity, wherein users can be kept in an active state (waiting to send or receive communications from the internet without the need to reconfigure the communication state and causing associated transmission delay losses). For wireless mobile communication systems, it is therefore required that the user consumes as little system resources as possible when not sending or receiving actual data traffic, while in this "ready" state. This supports maximizing the number of users that can remain in the ready state at any time.

For FDD enhanced uplink systems, each user unfortunately consumes valuable downlink coding resources when the user is in this "ready" state, since the need will arise because user-specific sequences have been allocated and reserved for the transmission of acknowledgement indicators.

Thus, current signaling techniques are not optimal. Any long-term allocation of downlink coding resources to each user for the purpose of acknowledgement signaling (regardless of their active state) would waste system resources, for example when only a few users are actively transmitting uplink data at any time and the remaining users are inactive.

Therefore, it would be advantageous to improve signaling within a cellular communication system. In particular, a system that allows for providing an improved acknowledgement process would be advantageous.

Disclosure of Invention

Accordingly, the invention seeks to preferably mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.

According to a first aspect of the present invention, there is provided an apparatus, e.g. a base station, for transmitting signalling information in a cellular communication system supporting a plurality of shared uplink transmission resources divided into sets of mutually exclusive transmission resources. The apparatus comprises means for granting uplink shared resources to a wireless subscriber communication unit by a grant message for uplink transmission. The apparatus comprises: means for receiving an uplink transmission from a wireless subscriber communication unit; means for deriving an uplink code resource identifier associated with an uplink transmission or grant message; means for allocating at least one downlink code sequence for carrying downlink signaling information associated with the derived uplink code resource identifier; and means for transmitting a downlink transmission including the at least one downlink code sequence to the wireless subscriber communication unit.

The shared resources may be defined in terms of codes (CDMA codes in CDMA systems or time-frequency codes in other multiple access systems) and time slots. In one embodiment, the system also supports multiple downlink shared resources that are divided into sets of mutually exclusive transmission resources. In the same manner as for the uplink, the shared downlink resources may be defined in terms of codes (CDMA codes in CDMA systems or time-frequency codes in other multiple access systems) and time slots.

The invention may allow an improved use of communication resources within a communication system. The invention may allow improved performance as perceived by the end user. The invention may provide increased capacity, reduced latency, and/or improved effective throughput.

The present invention may also support low latency retransmission schemes. In particular, the present invention may allow for "always-on" internet connectivity within a TDD system. The invention can facilitate supporting communication channels for a large number of users in a "ready state". The present invention may also avoid the need to reserve a code for a particular user on a long-term basis.

The invention may also allow the communication system to reuse resources that are not currently being used for other purposes or for other users. When the number scale of active users in a cell is increased, the invention can reduce the problem of coding resource management. The invention can avoid the need for higher layer of the communication protocol stack to allocate the E-HICH sequence. The invention can be compatible with some existing communication systems, such as a 3GPP TD-CDMA cellular communication system.

According to an optional feature of the invention, the means for allocating at least one downlink code sequence comprises associating an acknowledgement signal with the uplink code resource identifier such that the means for transmitting transmits a downlink transmission to the wireless subscriber communication unit comprising an acknowledgement signal associated with the derived uplink code resource identifier.

This allows for improved communication and may in particular allow for efficient coding resource usage during packet data transmission due to improved Acknowledgement (ACK)/Negative Acknowledgement (NACK) handling.

According to an optional feature of the invention, associating the acknowledgement signal with the derived uplink code resource identifier may be used in a TDD 3GPP system. According to another optional feature of the invention, the derivation of the uplink code resource identifier may be used in any Frequency Division Duplex (FDD) system in which uplink code resources are limited/restricted.

In accordance with an optional feature of the invention, the acknowledgement signal may be used within an enhanced uplink hybrid automatic repeat request (ARQ) identifier channel (E-HICH) within the 3GPP system. The present invention may reduce the number of users that undesirably consume downlink transmission resources (e.g., E-HICH) when not actively engaged in uplink transmissions.

According to an optional feature of the invention, the means for receiving comprises means for receiving an uplink transmission previously scheduled by the base station. The acknowledgement signal may be associated with a base station resource grant message, for example. This allows a one-to-one mapping of downlink "grant" channels for allocating resources to wireless subscriber communication units and corresponding downlink channels for transmitting ACK/NACK signals corresponding to the granted resources.

In accordance with an optional feature of the invention, the plurality of acknowledgement signals may be time division multiplexed or code division multiplexed on a single minimum transmission unit of Time Division Duplex (TDD) Code Division Multiple Access (CDMA). Typically, in a 3GPP TDD system, the smallest transmission unit comprises a single code of spreading factor 16 in a single time slot.

According to an optional feature of the invention, the means for allocating at least one downlink code sequence for carrying downlink signalling information associated with the derived uplink code resource identifier comprises associating a flag or identifier with substantially each actively transmitting user. This exploits the fact that typically (e.g. in a 3GPP system environment) the resource allocation tasks provided to each user will not overlap. Thus, in this way it can be ensured that the resource markers or identifiers may also be non-overlapping. Advantageously, this results in a further guarantee that each active user will be assigned a unique downlink E-HICH sequence.

This may allow for more efficient communication, e.g., may allow for better use of currently available resources, thereby facilitating a dynamic system when communication devices share resources.

According to an optional feature of the invention, the flag may be associated with substantially every actively transmitting user, wherein transmissions are performed within a single Transmission Time Interval (TTI). In accordance with an optional feature of the invention, the one or more tags identify one or more resource units spanning both the uplink and downlink portions of the communication frame. This may support that the association between the resource marker and the actual physical resource is not affected by a specific frame configuration or any uplink or downlink split point.

In accordance with an optional feature of the invention, the resource units are allocated to the transmitting user from, for example, "240" orthogonal sequences for 3GPP TDD operation. This may reduce payload waste. This may enable flexible selection of orthogonal coding sets for the E-HICH sequence used to carry the acknowledgement indicator.

According to an optional feature of the invention, a plurality of users are allocated a long downlink code sequence constructed using at least a two-stage serialized spreading process using at least two short code sequences. This may reduce the complexity of the wireless subscriber communication unit and its storage requirements. This may also enable flexible selection of orthogonal coding sets.

According to an optional feature of the invention, the invention may provide particularly advantageous system performance for an uplink packet data communication service, in particular an uplink packet data communication service.

According to a second aspect of the present invention there is provided a wireless subscriber communication unit for receiving signalling information in a cellular communication system supporting a plurality of shared uplink transmission resources divided into sets of mutually exclusive transmission resources. The wireless user communication resources include: means for receiving a downlink transmission from a base station, whereby the downlink transmission comprises at least one downlink code sequence for carrying downlink signaling information associated with a derived uplink code resource identifier related to a previous uplink transmission or a previous grant message.

According to a third aspect of the present invention, there is provided a method for transmitting signalling information in a cellular communication system supporting a plurality of shared uplink transmission resources divided into sets of mutually exclusive transmission resources. The method comprises the following steps: receiving an uplink transmission from the wireless subscriber communication unit by granting uplink resources to the wireless communication unit via a grant message; deriving an uplink code resource identifier from the uplink transmission or from the grant message; allocating at least one downlink code sequence for carrying downlink signalling information associated with the derived uplink code resource identifier; and transmitting a downlink transmission including the at least one downlink code sequence to the wireless subscriber communication unit.

According to a fourth aspect of the present invention, there is provided a method of receiving signalling information in a cellular communication system supporting a plurality of shared uplink transmission resources divided into sets of mutually exclusive transmission resources. The method comprises the following steps: receiving a downlink transmission from the base station, whereby the downlink transmission comprises at least one downlink code sequence for carrying downlink signalling information associated with the derived uplink code resource identifier in relation to a previous downlink transmission or a previous grant message.

According to a fifth aspect of the present invention there is provided a cellular communication system supporting a plurality of shared uplink transmission resources divided into sets of mutually exclusive transmission resources and adapted to support downlink transmissions from a base station to a wireless subscriber communication unit, whereby the downlink transmissions comprise at least one downlink code sequence associated with a derived uplink code resource identifier relating to a previous uplink transmission or a previous grant message.

According to an optional feature of the invention, the cellular communication system is a third generation partnership project, 3GPP, system. The 3GPP system may particularly be a UMTS cellular communication system. Thus, the invention may allow improved performance within a 3GPP cellular communication system.

The invention may allow improved performance in a TDD cellular communication system, and in particular may allow improved use of enhanced uplink systems in 3 GPP.

According to a sixth aspect of the present invention there is provided a wireless communications protocol supporting a downlink transmission from a base station to a wireless subscriber communication unit, whereby the downlink transmission comprises at least one downlink code sequence associated with a derived uplink code resource identifier relating to a previous uplink transmission or a previous grant message.

It will be appreciated that the optional features, comments and/or advantages described above with reference to an apparatus for transmitting uplink signalling information, such as a base station, are equally applicable to the method for transmitting uplink signalling information and that the optional features may be included in the method for transmitting uplink signalling information separately or in any combination.

It will be appreciated that the optional features, comments and/or advantages described above with reference to the wireless subscriber communication unit for receiving downlink signalling information apply equally to the method for receiving downlink signalling information and that the optional features may be included in the method for receiving downlink signalling information separately or in any combination.

These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to one or more embodiments described hereinafter.

Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

figure 1 illustrates an example of a cellular communication system in which some embodiments of the invention may be implemented;

figure 2 illustrates a UE, an RNC and a base station according to some embodiments of the invention;

FIG. 3 illustrates an example of using channelization and scrambling codes to generate data streams in accordance with some embodiments of the invention;

FIG. 4 illustrates an example of resource unit numbering according to some embodiments of the invention;

fig. 5 illustrates an example of E-HICH timing in accordance with enhanced uplink transmissions in accordance with some embodiments of the invention;

fig. 6 illustrates an example of spreading an Orthogonal Variable Spreading Factor (OVSF) code tree in accordance with some embodiments of the invention;

FIG. 7 illustrates an example of a Code Division Multiplexing (CDM) E-HICH burst structure in accordance with some embodiments of the invention;

FIG. 8 illustrates a serialized two-phase spreading operation in accordance with some embodiments of the invention;

fig. 9 illustrates a CDM transmitter structure for a TDD E-HICH in accordance with some embodiments of the invention; and

fig. 10 illustrates a method of transmitting and receiving signaling information according to some embodiments of the invention.

Detailed Description

The following description focuses on embodiments of the invention applicable to a UMTS (universal mobile telecommunications system) cellular communication system, in particular a UMTS Terrestrial Radio Access Network (UTRAN) operating in a Time Division Duplex (TDD) mode. It will be appreciated, however, that the invention is not limited to this particular cellular communication system and may also be applied to other cellular communication systems. In this respect, in one embodiment of the invention, the cellular communication system supports a plurality of shared uplink transmission resources that are divided into sets of mutually exclusive transmission resources.

Fig. 1 illustrates an example of a cellular communication system 100 in which embodiments of the invention may be implemented. In one embodiment of the invention, the cellular communication system 100 supports a plurality of shared uplink transmission resources that are divided into sets of mutually exclusive transmission resources. The shared uplink transmission resource may be defined in terms of codes and time slots. In this case, the coding may refer to a CDMA spreading sequence or scrambling sequence, or ordinary time-frequency coding within a time division multiplexed/code division multiplexed system. There are a limited number of codes and time slots, and thus any one unit within the overall shared resource space is defined by a time slot/code coordinate pair. The individual non-overlapping units of these shared resources may be further grouped together to form larger allocable resource units.

Within the cellular communication system 100, a geographic area is divided into a plurality of cells, each of which is served by a base station 105. The base stations, sometimes referred to as node bs, are interconnected by a fixed network that can transmit and receive data between the base stations and the core network 109. The wireless subscriber communication units 101, 103 are served by radio communication links with the base station 105 of the cell in which the wireless subscriber communication unit is located. A wireless subscriber communication unit is commonly referred to as a Mobile Station (MS) or a User Equipment (UE), which are to be considered interchangeable terms.

The wireless subscriber communication unit may be, for example, a remote unit, a mobile station, a communication terminal, a personal digital assistant, a portable computer, an embedded communication processor, or any communication unit that communicates over the air interface of the cellular communication system 100.

As the wireless subscriber communication unit 101, 103 moves, it may move from a communication coverage area supported by one base station 105 to a coverage area supported by another base station, i.e. from one cell to another. As the mobile stations 101, 103 move towards the base station 105, it enters the overlapping coverage area of the two base stations, within which it changes support by the new base station. As the mobile station moves further to a new cell, it continues to be supported by the new base station. This is called a handover or handoff of a mobile station between cells.

A typical cellular communication system extends the coverage area, typically over an entire country, comprising hundreds or even thousands of cells supporting thousands or even millions of mobile stations. Communication from a mobile station to a base station is referred to as uplink, and communication from a base station to a mobile station is referred to as downlink.

The base stations 105 are coupled to a Radio Network Controller (RNC) 107. The RNC 107 performs a number of control functions related to the air interface including radio resource management and routing of data to and from appropriate base stations.

The RNC 107 is coupled to a core network 109. The core network interconnecting RNCs are operable to route data between any two RNCs, thereby enabling a wireless subscriber communication unit in a cell to communicate with a wireless subscriber communication unit in any other cell. In addition, the core network 109 typically includes gateway functionality for interconnecting to external networks, such as the Public Switched Telephone Network (PSTN), thereby allowing wireless subscriber communication units to communicate with landline telephones and other communication terminals. Furthermore, the core network 109 comprises a number of functions required for managing a conventional cellular communication network, including functions for routing data, access control, resource allocation, subscriber billing, mobile station authentication, etc.

It will be appreciated that the specific elements of the cellular communication system 100 required to describe some embodiments of the present invention are illustrated for clarity and brevity only, but that the cellular communication system 100 may include many other elements, including other base stations and RNCs as well as other network entities such as SGSNs, GPRS Gateway Support Nodes (GGSNs), Home Location Registers (HLRs), Visitor Location Registers (VLRs), etc.

Conventionally, data scheduling over the air interface is performed by the RNC 107. However, it has been suggested that recent packet data services seek to use varying channel conditions when scheduling data on a shared channel. In particular, a High Speed Downlink Packet Access (HSDPA) service has recently been standardized by 3 GPP. HSDPA allows scheduling to be performed taking into account the downlink conditions of the individual UEs. Thus, data may be scheduled for a UE when channel propagation allows low downlink resource usage. However, to support this scheduling fast enough to follow dynamic changes, HSDPA requires that scheduling be performed on the base station rather than by the RNC. Locating the scheduling function within the base station avoids some communication components on the base station to the RNC interface (Iub interface), thereby reducing the significant delay associated therewith, especially in the case of retransmissions.

In the context of an enhanced uplink system, the uplink scheduling function is similarly moved from the RNC into the base station. In these systems, an acknowledgement signal is sent on the downlink to inform the transmitter (UE) of the reception status of the transmitted data packets. Advantageously, in one embodiment of the invention, this signaling method facilitates substantially zero usage of downlink coding resources for "ready but inactive" users. Thus, the method facilitates maintaining a large number of users in a ready state, improves system efficiency, and provides an "always-on" internet experience for an increased user base.

This approach takes advantage of the fact that users share channelization code resources on the TDD uplink (which is not the case for FDD within 3 GPP). Uplink data is block transmitted for a predetermined time period known to the user and the base station. These time periods are referred to as TTIs (transmission time intervals) and may include a plurality of slots. For TDD, the TTI is 10 milliseconds and is aligned with the 10 millisecond radio frame timing. One data block is transmitted per TTI and each data block returns an acknowledgement indicator.

The base station scheduler is responsible for allocating the uplink time slots and channelization code resources among the contending users for each TTI, as further described with reference to fig. 2. Each user to be active is granted a portion of the available uplink time slots and coding resources for scheduling in a given TTI. In one embodiment of the invention, a minimum Resource Unit (RU) is a single Spreading Factor (SF) -16 code within a single slot. Multiple minimum transmission units may be combined to form a larger resource allocation within any one TTI.

In one embodiment of the invention, multiple RUs may be allocated to a user in multiple time slots or multiple codes, even though current 3GPP specifications only allow up to two simultaneous codes within a given time slot. Alternatively, one or more channelization codes (e.g., SF8, SF4, SF2, and SF1) with lower or higher spreading factors such as multiple SFs 16 may be allocated within a time slot. Due to the structure of OVSF channelization codes used within 3GPP, multiple codes of higher spreading factor can be targeted to (dominant) common codes with lower spreading factor. This situation is illustrated subsequently in fig. 7, which illustrates a scenario according to the invention oneThe CDM E-HICH burst structure of some embodiments, whereinDenotes a channelization code with a spreading factor Q and an index i 1.

Assigning a first code with a first spreading factor excludes assigning any other UE with a spreading factor higher than the first spreading factor facing the first code. Thus, the codes assigned to users within the allocable shared uplink transmission resource space are specifically designed for use by a single user within a given TTI.

In terms of the overall uplink resource space, two-dimensional-slots and codes are defined. For a given TTI, there are a certain number of constituent slots and a certain number of coding resources available to be shared among competing users. Thus, there is a certain number of Resource Units (RUs) available per TTI.

In the following, some embodiments are described in which efficient transmission of acknowledgement/negative acknowledgement (ACK/NACK) signals is recommended. Accordingly, some embodiments result in improved scheduling performance, improved end-user perceived quality of service, and/or improved performance of the cellular communication system as a whole.

Fig. 2 illustrates in more detail the UE 101, RNC 107 and base station 105 of the example cellular communication system of fig. 1. The base station 105 comprises an uplink scheduler 221 for scheduling uplink transmission resources to active users within the cellular communication system. Uplink transmission resources are granted by sending a resource grant message from the uplink scheduler 221 to the UE 101 via the base transceiver station 220. The UE 101 receives the resource grant message through its transceiver 210 and transmits the grant information to the UE transmission controller 211. The transmission controller 211 is responsible for selecting data from the packet data transmission buffer 212 or the packet data retransmission buffer 213. User data for transmission is fed from a user data source 214 to the packet data transmission buffer 212 as needed. The transmission controller 211 is also able to move data from the packet data transmission buffer 212 into the packet data retransmission buffer 213 in the event that a negative acknowledgement indication has been received from the base station 105 relating to the data packet.

Upon receiving the transmission resource grant message, the transmission controller 211 thus selects data from the transmission buffer 212 or the retransmission buffer 213 as appropriate. In general, it may be preferable to prioritize retransmission over transmission. The transmission controller 211 transmits the data packet to the base station 105 through the transceiver 210 on the allocated one or more uplink resources.

The coding resources for transmission are configured by the transmission coding controller 215, which has been informed of the granted uplink coding resources by the transmission controller 211. The transmission controller 211 also sends a transmission resource grant message to the receiving code controller 216 which uses this information to derive the receiving code on which any "acknowledgement" indicator relating to the transmitted packet will be received.

In some embodiments, the allocation of at least one downlink code sequence associated with the derived uplink code resource identifier is dynamically allocated and reallocated in a short period of time (e.g., substantially on the order of a single radio frame or TTI-10 milliseconds).

The base station 105 receives the transmitted data packets on the previously granted resources and transmits the data to the received packet data buffer 222. Information related to the error status of the received packet is also transmitted to the uplink scheduler 221. The correctly received uplink data packets are sent to the RNC 107 via the base station to the RNC interface 223 and via the Iub interface. Received by the RNC 107 via the node-B interface 320. The uplink scheduler 221 may make further resource grants in an effort to recover the erroneous data through the retransmission process.

In either case, an acknowledgement indicator is generated based on whether the data packet was received in error. If the reception is deemed successful, a positive Acknowledgement (ACK) is sent by the transceiver 220. Otherwise a Negative Acknowledgement (NACK) is sent.

When determining that the uplink resources are granted, the uplink scheduler 221 also notifies the transport coding controller 224 of the allocated uplink coding resources. The transmit code controller 224 uses this information to derive the downlink code resources used to transmit the corresponding acknowledgement indicator. When an acknowledgement indicator is sent, the downlink code resources it uses are configured by the transport code controller 224 and thus associated with one or more uplink resources allocated for the relevant transmission of the acknowledgement indicator.

The transceiver 210 within the UE 101 has been pre-configured by the receive code controller 216 to detect the acknowledgement indicator sent by the base station 105. This pre-configuration of the reception coding resources may be supported by a previous reception of the original uplink resource grant and a known mapping within the UE between the uplink coding resources used for the transmission and the downlink coding resources used for the reception acknowledgement indicator. Thus, advantageously, no long-term allocation of downlink coding resources is required, and downlink coding resources are used only when uplink coding resources are used (i.e. when active uplink transmission occurs). Furthermore, any additional signaling overhead of allocating downlink coding resources, which may reduce system capacity, is avoided.

In an embodiment of the present invention, a base station 105 is provided that transmits signaling information within a time division multiplexed TD-CDMA cellular communication system. The base station 105 comprises means for receiving uplink transmissions from a wireless subscriber communication unit 101, such as a User Equipment (UE). Notably, the base station 105 includes means for deriving an uplink code resource identifier from the downlink transmission. The base station 105 further includes: means for allocating at least one downlink code sequence for carrying downlink signalling information associated with the derived uplink code resource identifier; and means for transmitting a downlink transmission comprising at least one downlink code sequence to the UE 101.

In one embodiment, the base station 105 associates the acknowledgement indicator code sequence with the code resources used in the corresponding uplink transmission. In an ACK/NACK transmission environment, this embodiment aims to address the above-mentioned disadvantages related to per-user code reservation in existing 3GPP FDD enhanced uplink systems within a 3GPP TDD system environment.

Fig. 3 illustrates an example of using channelization code 315 and scrambling code 325 to generate data stream 340 in accordance with some embodiments of the invention.

On a per user basis 305, 345, uplink data is transmitted by the wireless subscriber communication unit with one or more channelization code sequences to generate a channelization code spread signal. The channelized, encoded spread signal is multiplied by a scrambling code sequence 320 within a chip scrambling function 325 to generate a transmitted signal. The transmission signal is then sent over a radio channel 330 to a base station receiver 335, which demultiplexes the received user data stream 340.

Fig. 4 illustrates an example of resource unit numbering according to some embodiments of the invention. Fig. 4 illustrates an example of a situation where, for example, ten time slots 410 may be used for each radio frame of an enhanced uplink TTI transmission. The entire resource space 405 is available (size "16") in each time slot 410. Thus, there are a total of "160" RUs 430, numbered "0" through "159".

The base station scheduler implicitly knows which wireless user communication Units (UEs) have been allocated which time slots and coding resources for each TTI. For 3GPP TDD, these resource allocations are signaled to users within a downlink signaling channel (referred to as E-AGCH-enhanced uplink absolute grant channel within 3 GPP). Given that the resource allocation provided to each user cannot overlap with the resource allocation to another user, a unique resource index or "tag" can be advantageously associated with each active transmitting user in a given TTI.

The flag may correspond to any resource unit index assigned to a user, such as RU index "47" 425 (since the resource unit index may not have been assigned to any other user within the same TTI). For the sake of simplicity, it is assumed herein that the flag is set equal to the lowest-numbered RU allocated to the UE for the TTI of interest.

Thus, for example, if a UE is allocated the following coding resources for a particular TTI in a sixteen slot arrangement:

·1xSF4；

channelization code index 2;

specify enhanced uplink timeslots 1, 2, 3;

the flag assigned to this transmission will be the number '20' 435, the lowest numbered RU. Thus, this is the bottom left most allocated resource in FIG. 4 (the allocated resource is illustrated as a shaded box). It should be noted that in this example, a single allocation of one spreading factor 4 code within every 3 slots already occupies 4 minimum Resource Units (RUs) per slot. This is because RU is defined in this example as a single spreading factor 16 code, four of which correspond to a spreading factor 4 code within the OVSF code tree.

In one embodiment of the invention, the resource indicia associated with a user uplink transmission in a given TTI are used simultaneously by the base station and the wireless user communication unit to derive a code sequence index corresponding to the code used to transmit subsequent acknowledgement information relating to a previous uplink transmission. Thus, the base station knows on which code to send the acknowledgement indicator and the wireless subscriber communication unit knows when and where to expect the transmission and how to decode it.

This approach avoids the need to reserve a code for a particular user on a long-term basis. Advantageously, only actively transmitting users occupy acknowledgement indicator encoding resources.

It is envisaged that the method may be applied to any communication system in which the coding resources on the uplink channel are allocated separately. The above embodiments may be used, for example, if the channelization code resources in the FDD enhanced uplink are modified to a per user format.

In one embodiment, the TDD E-HICH is a physical channel that is transmitted once every TTI in a single slot and is configured to carry ACK/NACK information. Advantageously, the ACK/NACK information is synchronously related to the enhanced uplink TTI transmissions from a group of users.

This situation is illustrated in fig. 5, which illustrates an example of E-HICH timing associated with enhanced uplink transmission in accordance with some embodiments of the present invention. The timing association is illustrated as a code 505 versus time slot 510. For a particular frame "F", there are multiple downlink transmissions 515 and multiple uplink transmissions 520.

In one embodiment of the invention, the (single) E-HICH physical channel uses a spreading code of SF16 within a single downlink time slot per Transmission Time Interval (TTI). The E-HICH physical channel carries an acknowledgement indicator for each user in the E-HICH user group 525, respectively. The indicator Code Division Multiplexing (CDM) is within a single SF16 code.

A user group for which ACK/NACK information is transmitted at a specific E-HICH is referred to as an "E-HICH user group". These are active users. That is, for the enhanced uplink transmission 520 within the TTI (or frame) "F", an ACK/NACK is returned 530 on the E-HICH 535 downlink slot 540 within the TTI (or frame) "F + TA". Frame "F + TA" would thus include one or more E-HICH downlink transmissions 540 including an ACK/NACK indicator associated with the uplink transmission of frame "F," and may further include an uplink transmission 545.

Although the described embodiment is in the context of CDM of the acknowledgement indicator on the E-HICH channel, it is envisaged that alternative embodiments may be used in which the acknowledgement indicator is Time Division Multiplexed (TDM) on the E-HICH channel. Due to the inherent ability of CDM embodiments to support per-user power control while keeping the average slot power constant and equal to the training sequence (midamble) power, there may be some advantages of CDM schemes over TDM schemes.

Thus, according to an embodiment of the present invention, there is provided a wireless communication protocol supporting a downlink transmission from a base station to a wireless subscriber communication unit, whereby the downlink transmission comprises at least one downlink code sequence associated with a derived uplink code resource identifier related to a previous uplink transmission or a previous grant message.

In coding the downlink630 to E-HICH, one embodiment of the present invention can be considered as an extension of the OVSF code tree 600, as shown in fig. 6. There is a total of R corresponding to the E-HICH encoding 610_maxAnd may use orthogonal sequences 630. R_maxGreater than or equal to a total number of assignable shared uplink transmission resource units per TTI in the system for enhanced uplink transmission in the cell.

In one embodiment, a CDM E-HICH burst (burst) structure 700 may be configured as shown in FIG. 7. With respect to a conventional TDD burst, there are two payload portions 715, 730 of each user 705 divided by a training sequence (midamble) portion 720. Spare bits 725 distinguish the payload portions 715, 730 from the training sequence portion 720. A Guard Period (GP)735 is inserted at the end of the burst.

In this embodiment, a total of "240" orthogonal sequences are illustrated for TDD, such that RU numbering spans the uplink and downlink portions of the frame (16 resource units in each of the 15 slots per radio frame/TTI). Therefore, this configuration is not limited by a specific frame configuration or an Uplink (UL)/Downlink (DL) division point, etc. The choice of "240" also provides a good adaptation to the payload capacity of the SF16E-HICH physical channel ("244" bits for burst type "1" and "276" bits for burst type "2" in a 3GPP environment), with a lower waste of payload resources, but supports the use of the same structure for both burst types at the same time.

The selection of "240" also supports flexible selection of orthogonal coding sets. In one embodiment of the invention, it is desirable to be able to generate a length 240 code "on-the-fly" in order to avoid the need to store a complete code set of "240" x "240" (equal to 57.6 kilobits). In one embodiment, the length 240 code may be generated by a simple algorithmic means.

Advantageously, in an alternative embodiment, it is assumed that the code of length 240 can be generated from a smaller code set. Thus, for example, selecting "240" allows for the use of a serialized two-stage spread spectrum process 800, as shown in FIG. 8. This may reduce UE complexity and memory requirements.

For example, the embodiment shown in fig. 8 uses a serialized two-stage spreading operation, using sequence coding with two shorter orthogonal sequence sets, to generate a code of length "240". Thus, fig. 8 illustrates a first spreading phase having a spreading factor length of "20" bits and a second spreading phase having a spreading factor length of "12" bits according to some embodiments of the present invention. Here, an acknowledge or negative acknowledge single bit 805 is input to a first repetition block 810, wherein the single bit 805 is repeated twenty times. This repeated sequence is input to a first multiplication function 820 where it is multiplied by a primary code 815 of length "20".

The multiplied repeated sequence is then input to a second repetition block 825, where the repeated sequence is repeated twelve times. This repeated sequence is input to a second multiplication function 835 where it is multiplied by a primary code 830 of length "12". The subsequent output 840 is the desired 240-bit encoded group.

This embodiment therefore provides an efficient low complexity implementation in which the UE only needs to store one "12" and one "20" code group. Advantageously, this is significantly lower than "240" by "240". Thus, in this embodiment, a generic signature sequence length of "240" is used, regardless of the burst type, which simplifies implementation within the UE. The payload sizes for burst type "1" and burst type "2" are 244 bits and 276 bits, respectively, so there are four spare bits for burst type "1" and thirty-six spare bits for burst type "2". The processing gain loss due to these unused "spare" bits is small (i.e., determined to be 0.07dB and 0.6dB, respectively).

The skilled person will appreciate that more stages than two stages may be used to process. It is also assumed that alternative coding sets may be used depending on the target application, UE complexity reduction and storage requirements to be used.

A Code Division Multiplexing (CDM) transmitter structure 900 for a TDD E-HICH in accordance with some embodiments of the invention is illustrated in fig. 9. According to one embodiment, as shown in fig. 9, the primary code 815 may be constructed from rows of a Hadamard matrix having a row and column number of "20". Similarly, secondary encoding 830 may be constructed from rows of a Hadamard matrix with rows and columns of "12".

The coding index 815, 830 used in conjunction with the Hadamard matrix is derived from the following equation (i 0.., 19 for the primary coding group and j 0.., 11 for the secondary coding group):

j＝r mod 12 [2]

where "r" is the resource index marker described above. Furthermore, in some embodiments illustrated in fig. 9, row inversion modification and scrambling coding may be applied to Hadamard code groups 815, 830, for example using bit scrambling procedure 930 of 3GPP release 99. Such row inversion modification and scrambling may be applied after adding 925 any unused (spare) bits. Line inversion modification and scrambling codes can be used to improve their properties in terms of peak and average functions and to provide protection against doppler effects.

After applying the R99 bit scrambling code, the signal is Quadrature Phase Shift Keying (QPSK) modulated 935. The QPSK modulated signal is then multiplied with a user specified gain 940 within multiplier function 945. The resulting signal is then multiplexed with other user signals within multiplexer function 950. The E-HICH channelization code 955 is then applied to the multiplexed signal in a spreading function 960 that applies the spreading code of SF16 in one embodiment. The output signal is a CDMA transmission signal 965 of "1952" or "2208" chips, into which one or more training sequences (midambles) may be subsequently inserted.

In one embodiment of the present invention, a method 1000 of transmitting and receiving signaling information in a cellular communication system is described, as shown in fig. 10. The method includes the steps of communicating between a wireless subscriber communication unit 1050, such as a user equipment, and a base station 1010, such as a node B.

The method includes the node B1010 granting one or more uplink transmission resources to the UE 1050 in step 1015. In step 1055, the UE 1050 receives a grant of one or more uplink transmission resources. The UE 1050 then transmits an uplink message using all or a subset of the allocated one or more uplink resources, as illustrated in step 1060. At step 1020, node B1010 receives the uplink transmission.

Notably, the UE 1050 and the node B1010 derive a downlink code resource identifier from the grant message or the one or more uplink resources used simultaneously, as illustrated in steps 1065 and 1025. The node B1010 allocates at least one downlink code sequence for carrying downlink signalling information associated with the derived uplink code resource identifier and hence the uplink resources for uplink transmission. Further, the node B1010 then sends downlink signaling comprising at least one downlink code sequence to the UE 1050 using downlink resources derived from the granted or used uplink resources, as in step 1030. Then, in step 1070, the UE 1050 receives downlink signaling on one or more derived downlink resources, which can be decoded when it has independently derived the same downlink resources as the node B1010 from the one or more uplink resources granted or used.

In the context of the above description, and in accordance with embodiments of the present invention, the term "code sequence" is considered to encompass time sequences (e.g., as is common in CDMA systems), sinusoidal sequences equivalent to frequency subcarriers in other cellular communication systems (e.g., OFDM or FDMA), and common time/frequency coding in systems that use some combination of TDMA, FDMA and CDMA. In this way, embodiments of the present invention may be applied to other cellular communication systems in which users may be allocated resources in the form of time, frequency or time/frequency codes or sub-carriers of a primary carrier frequency.

It will be appreciated that the above description for clarity has described embodiments of the invention with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units or processors may be used without detracting from the invention. For example, functions illustrated to be performed by separate processors or controllers may be performed by the same processor or controller. Thus, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

The invention can be implemented in any suitable form including hardware, software, firmware or any combination of these. Alternatively, the invention may be implemented at least partly as computer software running on one or more data processors and/or digital signal processors. The elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Thus, the invention may be implemented in a single unit or may be physically and/or functionally distributed between different units and processors.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. The scope of the invention is limited only by the claims. Furthermore, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Furthermore, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category but rather indicates that the feature is equally applicable to other claim categories as appropriate. Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Moreover, the steps may be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus, references to "a", "an", "first", "second", etc. do not preclude a plurality.

Claims (16)

1. A wireless user communications unit for operation in a cellular communication system having a plurality of shared uplink transmission resources divided into mutually exclusive sets of uplink transmission resources and a plurality of shared downlink transmission resources divided into mutually exclusive sets of downlink transmission resources, the wireless user communications unit comprising:

a receiver unit configured to receive scheduling information comprising an allocation of uplink transmission resources from a network infrastructure device scheduled from the shared uplink transmission resources;

a control unit configured to derive an uplink resource identifier associated with a scheduled uplink transmission resource from the received scheduling information; and

a transmitter unit configured to transmit an uplink transmission using the scheduled uplink transmission resource, the uplink transmission including the uplink resource identifier;

wherein the control unit is configured to receive a downlink transmission associated with the uplink transmission on a downlink transmission resource determined from at least one of the received scheduled uplink resource or the uplink identifier.

2. The wireless subscriber communication unit of claim 1, wherein the receiver unit is configured to receive an acknowledgement signal via the downlink transmission resource, the acknowledgement signal being associated with an uplink resource identifier included in the uplink transmission.

3. The wireless subscriber communication unit of claim 1, wherein the transmitter unit is configured to operate to transmit the uplink transmission using a previously scheduled uplink transmission resource, the uplink resource identifier being derivable from the received uplink transmission.

4. The wireless subscriber communication unit of claim 1, wherein the receiver unit is configured to operate to receive the downlink transmission via downlink transmission resources that are dynamically allocated and reallocated in association with uplink code resource identifiers derived for a predetermined time period.

5. The wireless subscriber communication unit of claim 1, wherein a plurality of codes are linked to the grant allocation to support a plurality of resource grant channels.

6. The wireless subscriber communication unit of claim 5 wherein the plurality of acknowledgement signals are time division multiplexed or code division multiplexed onto a single minimum transmission unit of Time Division Duplex (TDD) Code Division Multiple Access (CDMA).

7. The wireless subscriber communication unit of claim 6, wherein said single minimum transmission unit is a code sequence using spreading factors of "16" or "32" within a time slot.

8. The wireless subscriber communication unit of claim 1, wherein the uplink resource identifier is derived using an uplink channelization code that has been dynamically allocated to the wireless subscriber communication unit.

9. The wireless subscriber communication unit of claim 1, wherein the receiver unit is configured to operate to receive downlink signalling information associated with the derived uplink resource identifier using a downlink transmission resource, the downlink signalling information being associated with a label for an actively transmitting wireless subscriber communication unit.

10. The wireless user communication unit of claim 9, wherein the indicia is for a single Transmission Time Interval (TTI).

11. The wireless subscriber communication unit of claim 9, wherein the flag identifies one of a plurality of resource units spanning uplink and downlink portions of a communication frame.

12. The wireless subscriber communication unit of claim 9, wherein the downlink transmission uses one of a set of "240" code sequences for TD-CDMA operation.

13. The wireless subscriber communication unit of claim 9, wherein the code sequence for the downlink transmission is constructed using at least two stages of serialized spreading processing.

14. The wireless subscriber communication unit of claim 1, wherein the uplink transmission is a unique set of frequency division duplex uplink transmissions supporting uplink shared resources.

15. The wireless subscriber communication unit of claim 1, wherein the uplink transmission is an enhanced uplink transmission within a time division duplex system.

16. The wireless subscriber communication unit of claim 1, wherein said cellular communication system is a third generation partnership project (3GPP) system.