It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

Random matrix theory has found many applications in physics, statistics and engineering since its inception. Although early developments were motivated by practical experimental problems, random matrices are now used in fields as diverse as Riemann hypothesis, stochastic differential equations, condensed matter physics, statistical physics, chaotic systems, numerical linear algebra, neural networks, multivariate statistics, information theory, signal processing and small-world networks. This article provides a tutorial on random matrices which provides an overview of the theory and brings together in one source the most significant results recently obtained. Furthermore, the application of random matrix theory to the fundamental limits of wireless communication channels is described in depth.

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Random Matrix Theory and Wireless Communications

A system and method for communicating information signals using spread spectrum communication techniques. PN sequences are constructed that provide orthogonality between the users so that mutual interference will be reduced, allowing higher capacity and better link performance. With orthogonal PN codes, the cross-correlation is zero over a predetermined time interval, resulting in no interference between the orthogonal codes, provided only that the code time frames are time aligned with each other. In an exemplary embodiment, signals are communicated between a cell-site and mobile units using direct sequence spread spectrum communication signals. In the cell-to-mobile link, pilot, sync, paging and voice channels are defined. Information communicated on the cell-to-mobile link channels are, in general, encoded, interleaved, bi-phase shift key (BPSK) modulated with orthogonal covering of each BPSK symbol along with quadrature phase shift key (QPSK) spreading of the covered symbols. In the mobile-to-cell link, access and voice channels are defined. Information communicated on the mobile-to-cell link channels are, in general, encoded, interleaved, orthogonal signaling along with QPSK spreading.

System and method for generating signal waveforms in a CDMA cellular telephone system

Massive multiple-input multiple-output MIMO is one of themost promising technologies for the next generation of wirelesscommunication networks because it has the potential to providegame-changing improvements in spectral efficiency SE and energyefficiency EE. This monograph summarizes many years ofresearch insights in a clear and self-contained way and providesthe reader with the necessary knowledge and mathematical toolsto carry out independent research in this area. Starting froma rigorous definition of Massive MIMO, the monograph coversthe important aspects of channel estimation, SE, EE, hardwareefficiency HE, and various practical deployment considerations.From the beginning, a very general, yet tractable, canonical systemmodel with spatial channel correlation is introduced. This modelis used to realistically assess the SE and EE, and is later extendedto also include the impact of hardware impairments. Owing tothis rigorous modeling approach, a lot of classic "wisdom" aboutMassive MIMO, based on too simplistic system models, is shownto be questionable.

https://www.nowpublishers.com/article/DownloadSummary/SIG-093

Massive MIMO Networks: Spectral, Energy, and Hardware Efficiency

We investigate robust wireless communication in high-scattering propagation environments using multi-element antenna arrays (MEAs) at both transmit and receive sites. A simplified, but highly spectrally efficient space-time communication processing method is presented. The user's bit stream is mapped to a vector of independently modulated equal bit-rate signal components that are simultaneously transmitted in the same band. A detection algorithm similar to multiuser detection is employed to detect the signal components in white Gaussian noise (WGN). For a large number of antennas, a more efficient architecture can offer no more than about 40% more capacity than the simple architecture presented. A testbed that is now being completed operates at 1.9 GHz with up to 16 quadrature amplitude modulation (QAM) transmitters and 16 receive antennas. Under ideal operation at 18 dB signal-to-noise ratio (SNR), using 12 transmit antennas and 16 receive antennas (even with uncoded communication), the theoretical spectral efficiency is 36 bit/s/Hz, whereas the Shannon capacity is 71.1 bit/s/Hz. The 36 bits per vector symbol, which corresponds to over 200 billion constellation points, assumes a 5% block error rate (BLER) for 100 vector symbol bursts.

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Simplified processing for high spectral efficiency wireless communication employing multi-element arrays

A wireless debit card communications system comprising a radio unit, a base station, and an end station. The radio unit, for example, a radio telephone, includes a first processor, a reader for reading a credit amount and a personal access number from a debit card, and a transceiver for communicating, using radio waves, a credit signal. The base station receives and relays the credit signal over a communications channel to the end station. The end station includes a switch to generate a first control signal to allocate the credit amount of the debit card to the radio unit, and to set a radio unit access number of the radio unit to the personal access number of the debit card with a communications path through the base station. The end station also generates a second control signal for changing the credit amount and the personal access number of the debit card. The base station may be connected to a debit meter. The radio unit and the debit meter respond to the second control signal to change the credit amount and the personal access number using magnetic writers or writer processors to store an updated credit amount and personal access number on a magnetic strip on a debit card or on a chip on the debit card as the debit card is used in the radio unit. The personal access number may be used as a telephone number of the radio unit.

Wireless telephone debit card system and method

A new family of multistage low-complexity linear receivers for direct sequence code division multiple access (DS-CDMA) communications is introduced. The objective of the proposed design is to mitigate the effect of multiple access interference (MAI), the most significant limiting factor of user capacity in the conventional DS-CDMA channel. The receivers presented here employ joint detection of multiple users and therefore require knowledge of all the signature codes and their timing. In addition, for a multipath environment, reliable estimates of the received powers and phases are assumed available for maximal ratio RAKE combining. Each stage of the underlying design recreates the overall modulation, noiseless channel, and demodulation process. The outputs of these stages are then linearly combined. The combining weights can be chosen to implement different linear detectors, including the decorrelating and minimum mean square error (MMSE) detectors. In this paper, we focus on implementing the MMSE detector. Simulation results illustrate that significant performance gains can be achieved in both synchronous and asynchronous systems.

Multistage linear receivers for DS-CDMA systems

A spread-spectrum transmitter and receiver using code division multiple access with time division multiple access technology for spread-spectrum communications. At a base station, a spread-spectrum transmitter includes a multiplexer for time multiplexing a synchronization-code signal and a plurality of data signals, which may be encoded as a plurality-encoded data signals, to generate a time-multiplexed signal. A chip code generator generates a chip-code signal which is modulo added with the time-multiplexed signal by an EXCLUSIVE-OR gate to generate a spread-spectrum-time-multiplexed signal. A transmitter transmits the spread-spectrum-time-multiplexed signal over a communications channel. A spread-spectrum receiver at the base station processes a plurality of spread-spectrum signals, received from a plurality of remote units in as time division sequence of spread-spectrum signals, using a despreader circuit to generate a time-division signal. A demultiplexer demultiplexes the time-division signal as a plurality of data signals or as a plurality of privacy-encoded data signals. A remote unit, which may be a handset, includes a despreader circuit for despreading the spread-spectrum-time-multiplexed signal as a time-multiplexed signal. A synchronization-code matched filter detects the synchronization-code signal embedded in the time-multiplexed signal and thereby generates a timing signal. A controller uses the timing signal to generate a control signal. The control signal controls a transmit-receive switch for switching an antenna between the despreader circuit to the transmitter at the remote unit.

CDMA/TDMA spread-spectrum communications system and method

A spread-spectrum CDMA communications system for locating remote units, and for communicating message data between a plurality of remote units and a base station. The spread-spectrum CDMA communications system includes a plurality of base stations and a plurality of remote units. A base station has a spread-spectrum modulator for spread-spectrum processing the message data, and a transmitter for transmitting the spread-spectrum processed-message data, combined with a generic-chip-code signal, from the base station to a remote unit. The base station also has an antenna, and spread-spectrum detectors for recovering message-data communicated from the remote-units. A remote-unit has an antenna, and a detector coupled to the antenna for recovering data communicated from the base station. The detector includes a spread spectrum demodulator. Also, the remote unit has a device for converting the format of the data into a form suitable for communicating over radio waves, a spread spectrum modulator and a transmitter. The base station has a range circuit, which comparers the generic-chip-code signal generated at the base station with the generic-chip-code signal received from the remote unit, for determining a range between the remote unit and the base station.

CDMA communications and geolocation system and method

A spread spectrum communications system for use over a communication channel, including a transmitter-generic-chip-code generator (101), a transmitter-message-chip-code generator (102), an EXCLUSIVE-OR gate (103), a combiner (104), a transmitter (107), a receiver-generic-chip-code generator (121), a receiver-generic mixer (123), a generic-bandpass filter (125), a receiver-message-chip-code generator (122), a receiver-message mixer (124), a message-bandpass filter (126), and a synchronous detector (139). The transmitter-generic-chip-code generator (101) generates a generic-chip-code signal and the transmitter-message-chip-code generator (102) generates a message-chip-code signal. The EXCLUSIVE-OR gate (103) spread-spectrum processes message data with the message-chip-code signal to generate a spread-spectrum signal. The combiner (104) combines the generic-chip-code signal with the spread-spectrum signal. The transmitter (107) transmits the combined generic-chip-code signal and spread-spectrum signal, on a carrier signal (108) over the communications channel as a spread-spectrum-communications signal. The receiver-generic-chip-code generator (121) generates a replica of the generic-chip-code signal. The generic mixer (123) recovers the carrier signal from the spread-spectrum-communications signal. The receiver-message-chip-code generator (122) generates a replica of the message-chip-code signal. The receiver-message mixer (124) despreads the spread-spectrum-communications signal as a modulated-data signal. The tracking and acquisition circuit (121) uses the recovered carrier signal for synchronizing the replicas of the generic-chip-code signal to the recovered carrier signal. The synchronous detector (139) synchronously demodulates the modulated-data signal as received data.

Donald L. Schilling

Papers

Wireless telephone debit card system and method

Multistage linear receivers for DS-CDMA systems

CDMA/TDMA spread-spectrum communications system and method

CDMA communications and geolocation system and method

Synchronous spread-spectrum communications system and method