Lucent Technologies Inc.

Rajeev Krishnamoorthy

Harish Viswanathan

Markus Rupp

Shankar Narayanaswamy

Xiaodong Li

Jeffrey Paul Grundvig

Richard Dennis Gitlin

Howard C Huang

Dale Harvey Nelson

Reinaldo A Valenzuela

Hui-Ling Lou

Pamela C Kwong

Thomas A Gentles

In a TDMA system a multifunction control channel is employed that carries data used for implementing channel access functionality for users and is also employed at the remote terminals in the performance of modem functionality. In other words, information necessary to accurately receive data on the user traffic channels is obtainable by processing the multifunction control channel. This is achieved by arranging the broadband channel of the TDMA system as a repeating frame having time slots in which at least one time slot is reserved for use as the multifunction control channel, and the data that is transmitted on the multifunction control channel is encoded using a spread spectrum format. To this end the data carried on the multifunction control channel is encoded in a way that uses each symbol of the multifunction control channel as if it were a so-called spread spectrum 'chip'. At least one of the remaining time slots of the frame, and preferably all of the remaining time slots, which are typically used to carry user traffic arranged as logical channels, are not spread spectrum encoded. With regard to modem functionality, the remote terminals use the received multifunction control channel to a) perform frame synchronization, i.e., frame timing, b) perform frequency offset estimation, c) obtain an estimate of the channel impulse response, and d) estimate the received signal strength for use in gain control.

Control channel for time division multiple access systems

In a wireless communication system, the constellation mapping scheme employed may be changed on a per-time-slot basis, i.e., from time slot to time slot, so that the constellation used to encode the symbols of each time slot may be different for each time slot within a single frame and may be different for a particular time slot in different consecutive frames. In other words, several constellation mapping schemes are available, with each providing the ability to transmit a different number of bits per symbol, and the particular constellation mapping scheme employed for any time slot need be selected for that time slot only. The ability to use any particular constellation mapping scheme is dependent on the current channel quality. The particular constellation mapping used for the user data of the time slot may be indicated in the preamble of the time slot. To this end, each time slot may have its own preamble that is mapped with a constellation mapping scheme which is a) known &agrave; priori, b) may be the same for all time slots, and c) may be different from the constellation mapping scheme used to encode user data in the time slot. A receiver can determine the constellation mapping used for each time slot from solely from the preamble of the time slot.

Demodulation method for receiver

In a system in which the modulation scheme employed may change on a per-time-slot basis, a user's available data rate may change even if the user maintains the same number of time slots, because the capacity of the user's time slots may change. If one or more such changes in modulation scheme occurs, the data rate available to the user may no longer match his current data rate needs. Therefore, a method is disclosed for determining the number of time slots to assign to a user as a function of the user's current data rate requirement and the actual current cumulative data rate of the time slots currently assigned to the user. The user data rate requirement may further be a function of a quality of service (QoS) contracted for by the user. Thus, the assignment of the time slots within the frame is made dynamically and the number of time slots employed by a user is increased or decreased according to the user's current data rate requirements and the ability of the time slots already assigned to the user to meet those requirements.

Medium allocation method

A two layered segmentation technique coupled with a two layer error detection technique is used to implement the wired to wireless network interface. A wireless network divides network layer packets from a wired network into radio data link packets, and the information within the radio data link packets is divided into portions that can be placed into time slots. Error detection is performed on each of the time slots and also at the radio data link packet level to determine if there is an error within the radio data link packet. Errors detected in any radio data link packet only requires retransmission of the radio data link packet in which the error was detected, and, advantageously, do not require retransmission of the entire network layer packet as would have been required in a system that mapped directly from network layer packets to time slots. Further advantageously, the system is able to be employed by systems that utilize dynamic constellation mapping schemes which result in different time slots for the same user being mapped with different constellations, and so they have different bit to symbol ratios. This is because such changes in the constellation mapping scheme are handled at the time slot level, and are not seen at the radio data link packet level. The segmentation of the network layer packets into radio link packets is independent of the number and size of the time slots which will carry the radio link packets.

Data link protocol for wireless systems

In a wireless communication system, the constellation mapping scheme employed may be changed on a per-time-slot basis, i.e., from time slot to time slot, so that the constellation used to encode the symbols of each time slot may be different for each time slot within a single frame and may be different for a particular time slot in different consecutive frames. In other words, several constellation mapping schemes are available, with each providing the ability to transmit a different number of bits per symbol, and the particular constellation mapping scheme employed for any time slot need be selected for that time slot only. The ability to use any particular constellation mapping scheme is dependent on the current channel quality. The particular constellation mapping used for the user data of the time slot may be indicated in the preamble of the time slot. To this end, each time slot may have its own preamble that is mapped with a constellation mapping scheme which is a) known a priori, b) may be the same for all time slots, and c) may be different from the constellation mapping scheme used to encode user data in the time slot. A receiver can determine the constellation mapping used for each time slot from solely from the preamble of the time slot.

Modulation method for transmitter

Multiple microcell base stations are located within a macrocell having single macrocell base station in an hierarchical architecture, and microcell users (&mgr;-users) and macrocell users (M-users) communicate respectively with the &mgr;-base and the M-base using the same frequency band, by appropriately (a) selecting the ratio of the radius r of each &mgr; cell and the average distance d from the M-base (r and d are measured by the &ldquo;radio distance&rdquo;, which includes the effects of shadowing), and (b) controlling the power level with which uplink (mobile to base) and downlink (base to mobile) messages are communicated. Typically, &mgr;-cell size and location are chosen such that d/r>10. With respect to uplink communications, the transmit powers of the &mgr;-users in a &mgr;-cell are controlled so that the total received power at the nearest M-base is equivalent to the received power from C M-users, where C is usually set to unity. As a result, the M-cell basically loses C users worth of capacity, but the total number of users is increased by virtue of the additional &mgr;-users. With respect to downlink communications, as long as the microbase and the macrobase are coordinated systems, the &mgr;-base transmit power is controlled so that at the point of handoff between a &mgr;-base and M-base, the received power at a user from the two bases is equivalent, and the received power at the bases from this user is also equivalent. With this arrangement, the &mgr;-base transmit power is increased as r grows and d decreases in order for this balance to occur. Where the M-base and &mgr;-base have no knowledge of each other and handoffs are not allowed between the two base types, a family of I/Q short codes which are quasi-orthogonal to the existing short (pilot) codes are generated, and these codes are used to distinguish between the M-base and &mgr;-base signals.

Power control and cell site location technique for CDMA systems with hierarchical architecture

Parallel Decision-Feedback Decoding (PDFD) techniques which provide joint Decision Feedback Equalization (DFE) and decoding of a sequence of transmitted symbols. In an illustrative embodiment, branch metrics associated with transitions between states of a multi-stage trellis are computed. For a given stage t of the trellis, the branch metrics are computed for each of the states, using a different input value y (s) for each state. The input values y (s) correspond to extended survivor paths computed for each state using a DFE process. The branch metrics are utilized to determine a global most-likely path through the trellis, and the path is used to generate a decoded output signal representative of the transmitted symbol sequence. The PDFD techniques of the invention provide significant performance gains relative to conventional techniques, and are suitable for use with both PSK and QAM modulation constellations.

Methods and apparatus for parallel decision-feedback decoding in a communication system

A method of transmitting a voice communications signal includes the steps of sampling the signal and creating digital representations of the samples. The digital representations are speech-coded to create speech-coded data which is converted to analog symbols. A carrier in the 46-49 MHz band is modulated by the analog symbols and transmitted. A method of receiving a voice communications signal includes the steps of receiving a modulated carrier in the 46-49 MHz band and demodulating the modulated carrier to recover analog symbols. The analog symbols are converted to digital samples, which are then converted to speech-coded data. The speech-coded data are decoded to produce digitized samples, which are converted to analog samples and filtered to produce the voice communications signal. A cordless telephone system according to the invention includes a handset and a base unit. The handset includes a microphone, a speaker, a first digital signal processor connected to the microphone and to the speaker, a first 46-49 MHz RF transceiver connected to the first digital signal processor, and a first antenna connected to the first 46-49 MHz transceiver. The base unit includes a second antenna, a second 46-49 MHz RF transceiver connected to the second antenna, a memory, and a second digital signal processor connected to the second 46-49 MHz RF transceiver, to the memory, and to a telephone line interface.

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Middletown, NJ, United States of America

Rajeev Krishnamoorthy