Nortel Networks Corporation

Other

Bassam M Hashem

Shalini Suresh Periyalwar

David G Steer

Yoon Chae Cheong

Mark Earnshaw

Hang Zhang

Koon Hoo Teo

Eman A Fituri

Norman P Secord

Wookwon Lee

Mo-Han Fong

Leo L Strawczynski

Gamini Senarath

John Edward Hudson

Daniel Boudreau

Farideh Khaleghi

Robert Matyas

Anatoli V Kotov

A method and apparatus are provided for selecting an optimum base station for communicating with a terminal in a wireless communication system. A base station controller stores two candidate sets for each terminal within communication range of the base stations controlled by the base station controller. One candidate set lists base stations for which the channel quality of the uplink channel between the base station and the terminal is acceptable for communication. The other candidate set lists base stations for which the channel quality of the downlink channel between is acceptable for communication. This allows the base station controller to take into account the predominant direction of traffic when assigning base stations for communication with the terminal.

Packet communication system with dual candidate sets for independent management of uplink and downlink transmissions

The present invention keeps track of channel change indicia associated with wireless communications with mobile terminals, and bases the scheduling of data in time slots of a scheduling period on the channel change indicia. The channel change indicia may be derived from any information that bears on the rate at which channel conditions are likely to change, such as the velocity the mobile terminals are traveling or actual channel condition measurements. Preferably, mobile terminals associated with intermediate values for the channel change indicia are given priority, and thus, scheduled for transmission before those with lower and higher values. The invention is applicable to uplink and downlink communications, and is particularly beneficial when implemented in uplink and downlink schedulers in a base station.

Scheduling based on channel change indicia

A multiplexer function maintains a transmission table of all link control frames sent to a physical layer for transmission to a receiver. The transmission table includes a list of frames from various link control entities in the order in which they were multiplexed together to form a stream of frames. At the receiver, when a frame is detected that is in error, the physical layer sends an indication to its associated demultiplexer function, which sets a timer. When the timer expires, the demultiplexer function issues a message, such as a negative acknowledgement message, directly to the sender via the physical layer. The message includes information about the link control frames preceding and following the errant frame. The identified frames may be associated with different link control entities, and are preferably provided in the order in which they were received. The multiplexer function compares the identified frames in the message to the list of frames in the transmission table to identify the errant frame or frames and operates to effect retransmission of the errant frame.

Efficient frame retransmission in a wireless communication environment

A method and apparatus are provided for selecting and signalling the identity of sub-carriers to be used for transmission of data in a radio communication system, and for using other sub-carriers. A remote unit determines which sub-carriers are acceptable for use in data transmission by comparing the signal to interference ratio of each sub-carrier with a threshold. A sequence of numbers is generated using one set of values to identify acceptable sub-carriers and another set of values to identify unacceptable sub-carriers. The sequence of numbers is transmitted to a base station. The average signal to interference ratio of sub-carriers whose signal to interference ratio was above the threshold can also be transmitted to the base station, thereby allowing the base station to determine an optimum set of transmission parameters for use only in the acceptable sub-carriers. Alternatively, the remote unit can determine the optimum set of transmission parameters itself for transmission to the base station. As yet another alternative, the remote unit can determine an optimum Link Mode for each acceptable sub-carrier, and use a reference to the Link Modes as the set of values identifying acceptable sub-carriers. The base station transmits data over the acceptable sub-carriers at the optimum Link Mode or Link Modes. The base station may use some of the unacceptable sub-carriers for transmission of low sensitivity data at the optimum Link Mode, and may use some of the unacceptable sub-carriers for transmission of data at a lower Link Mode. The transmission power of any unused unacceptable sub-carriers can be diverted to other sub-carriers.

Dynamic sub-carrier assignment of OFDM systems

A wireless communication system () includes a network (), one or more mobile stations (), and a medium access control (MAC) protocol (). The MAC protocol () includes a state transition design () and a control channel design (). The state transition design () includes null (), dormant (), standby (), and active states () for each mobile station (). The control channel design () includes a common control channel (), a slow control channel () and a fast control channel (), and is adapted to control communications from the network to each mobile station.

Medium access control (MAC) protocol for a wireless communication system

A method and apparatus are provided for error correction in a communication system employing Orthogonal Frequency Division Multiplexing. When a remote unit receives an OFDM symbol, a retransmission indicator bit is examined to determine whether the symbol is an original symbol or a retransmitted symbol. If it is a retransmitted symbol and the remote unit has a corresponding symbol stored in memory, then the received symbol is soft-combined with the stored symbol. Each packet in the symbol, either the received symbol if original or the soft-combined symbol if retransmitted, is examined by the remote unit. If the remote unit determines that a particular packet is intended for the remote unit, but can not determine the contents of the payload of the packet, the remote unit sends a retransmission request to the base station for retransmission of the symbol. The base station determines whether the entire symbol or merely the packet should be retransmitted, based on such considerations as the size of the packet or whether there are additional requests for the symbol. The invention allows both soft-symbol combining and Automatic Repeat Request to be used as error correction techniques.

Enhanced ARQ with OFDM modulation symbols

It is becoming increasingly important to improve data throughput in wireless networks. By transmitting data simultaneously at different modulation amplitudes and/or using different code strengths, terminals having different carrier to noise ratios are able to decode the different amplitude levels with varying degrees of success. This allows distant terminals to receive low data rate transmissions at high modulation levels or code rates while nearer terminals can use additional capacity in the transmission by receiving lower level modulation signals or code rates. In this way, distant terminals do not degrade overall network performance. By arranging for terminals to acknowledge receipt of data, retransmission at different modulation levels or code rates may be carried out by the base station in order to improve performance in the presence of noise without a priori knowledge of the carrier to noise ratio for a particular terminal.

Methods and apparatus for transmitting and receiving data over a communications network in the presence of interference

The present invention relates to a method and apparatus for reducing interference arising from signal propagation delay in multipath signal environments in wireless communication systems. The present invention provides a method of operating a mobile communications base station which receives multipath components of signals from a number of high mobility subscriber terminals, the method comprising: for each subscriber terminal signal received, determining a best signal component; determining the difference in time between reception of said best signal component and a reference time; transmitting to said terminal a transmission timing offset in order to receive said best component at substantially said reference time.

Method and apparatus for using synchronous CDMA in a mobile environment

The present invention relates to a link control automatic repeat request (ARQ) operation in a wireless communication environment. When a terminal sends an original request for communication resources, the request includes not only payload size, but preferably quality of service parameters associated with the data to be transmitted. During uplink communications, the base station performs the link control based ARQ for lost or corrupt packets. When lost or corrupt packets are identified, a link control entity at the base station determines the appropriate retransmission parameters and contacts the uplink scheduler, if necessary, to obtain the corresponding communication resources for retransmission. The additional communication resources for retransmission are provided in a message, such as a negative acknowledgement message, which is sent to the mobile terminal to trigger retransmission of the lost or corrupted data.

A method and apparatus for assigning a time slotted code division multiple access carrier for wireless reverse link communication between a device and a base station. One or more performance characteristics corresponding to the device are determined. A code division multiple access spreading code is assigned based on the determined performance characteristics. A time slot for communication with the base station is assigned based on the assigned spreading code. According to one aspect, the assigned spreading code corresponds to one of an SCDMA code and an ACDMA code such that a time slot corresponding to an SCDMA code provides a time slot in which all devices are preferably in time-aligned orthogonal communication with the base station. An increase in channel gain and an increase in channel capacity result as compared with a system where time slots support mixed ACDMA and SCDMA codes.

System and method for time slotted code division multiple access communication in a wireless communication environment

Dynamic sub-carrier assignment in OFDM systems

A method, device and base station for using a code division multiple access carrier for wireless reverse link communication between the device and the base station. An operational profile of the device is determined in which the operational profile includes a degree of unit mobility. A first carrier for wireless code division multiple access communication from the device to the base station is selected based on the determined operational profile of the device. A wireless communication link between the device and the base station is established using the first carrier. According to one aspect, the first carrier is one of an asynchronous code division multiple access signal and a synchronous code division multiple access signal.

System and method for code division multiple access communication in a wireless communication environment

Methods, receivers and transmitters all adapted to assist in the performance of layer 2 frame delineation are provided which are applicable in the context of OFDM, and also applicable to any layer 1 design facilitating high data rate transmission. Advantageously, the invention allows the identification of where a layer 2 frame begins notwithstanding the fact that the previous layer 2 header, which would normally be used to identify the location of the next layer 2 frame, has been received in error. As a consequence, rather than discarding considerable quantities of data after an erroneous header, for example all data until a super-frame boundary, layer 2 frames can be correctly received staring with the next header received in a non-erroneous layer 1 frame.

System and method for layer 2 frame delineation recovery

A method and system for selecting a station, in a communication system having a plurality of stations, for communication with a device based on station load conditions is provided. A plurality of base stations determine their station load condition. Station transmit power level is adjusted for at least a part of a transmitted signal in each of the plurality of stations in accordance with the respective determined station load condition. A device receives the transmitted signal from at least one of the plurality of stations and selects a station for communication. The station selection is made by the device based at least in part on a received power level of the adjusted portion of the transmitted signal.

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Nepean, Canada

Bassam M Hashem