EP0719003A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Frequency hopped cellular mobile radio system combining OFDM and frequency hopping
Assignee: Roke Manor Research Ltd
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Filing: 1995-11-17
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Granted: —
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Expires: 2015-11-17
Abstract
Abstract CDMA cellular mobile radio using frequency hopping has been shown to yield very high spectral efficiencies. Known systems involve long interleaving delays to obtain adequate interferer diversity. This invention involves the use of faster frequency hopping (a few bits per hop) to achieve good interferer diversity without the need for long delays. The use of DBPSK along with a QPSK element to randomise interference achieves good performance. Error correction coding is applied with interleaving to average over the different interferer. Orthogonal frequency division multiple access provides for higher spectral efficiency and provides very simple implementation.
Inventors
- 👤 Anthony Peter Hulbert
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 12:56
CPC Classifications
H; H04; H04L; H04L1/00; H04L1/004; H04L1/0056; H04L1/0071; H04B; H04B1/00; H04B1/69; H04B1/713; H04L27/00; H04L27/26; H04L27/2601; H04L27/2602; H04L27/2626; H04L27/2647; H04L27/2649; H04L27/26524; H04B1/7136; H04B2001/71365; H04B2001/71367
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
70 words
A frequency hopped cellular mobile radio system comprising at least one base station and a plurality of terminals, each terminal being arranged to communicate with said base station over a radio medium, wherein the terminals are arranged to operate using orthogonal frequency division multiple access techniques, in which the terminals transmit orthogonally on a number of different frequencies, so that one or more data streams are multiplexed onto orthogonal frequencies.
Claim 2
Dependent Claim
30 words
A system as claimed in Claim 1, wherein the orthogonal frequencies have a uniform frequency spacing f c and linear signalling is applied at the rate of 1/f c .
Claim 3
Dependent Claim
54 words
A system as claimed in Claim 2, wherein the system is arranged to utilise synchronised orthogonal slow frequency hopping with orthogonal frequency division multiple access, so that each terminal alters its transmit frequency from one frequency to another, which in the case of an uplink cellular mobile radio system, fully orthogonal transmission is achieved.
Claim 4
Dependent Claim
45 words
A system as claimed in Claim 2 or Claim 3, wherein each mobile terminal includes means to affiliate that terminal to their nearest base station and means to control the power so that the minimum power is used to achieve adequate bit error rate performance.
Claim 5
Independent Claim
29 words
A system as claimed in any preceding claim, wherein forward error correction coding means is provided to average the effects of poor signal conditions over the good signal conditions.
Claim 6
Dependent Claim
16 words
A system as claimed in Claim 5, wherein the forward error correction coding uses convolutional codes.
Claim 7
Dependent Claim
17 words
A system as claimed in Claim 5, wherein the forward error correction coding uses Reed Solomon codes.
Claim 8
Dependent Claim
141 words
A system as claimed in Claim 5, wherein each terminal includes an antenna via which radio communication is achieved to each base station, a downlink receiver connected to said antenna and demultiplexing means for demultiplexing an output from said downlink receiver, said demultiplexing means being arranged to advance or retard a clock generation means which is arranged to control the timing of transmitted symbols produced by forward error correction coding means with reference symbols inserted in the coded data stream, the output of which is passed to a pair of digital synthesisers, each arranged to be controlled by a hopping sequence generator, a first digital synthesiser being dedicated to inphase signals and the second digital synthesiser being dedicated to quadrature phase signals, and means for modulating the output from said digital synthesisers onto a carrier frequency for transmission to said antenna.
Claim 9
Independent Claim
118 words
A system as claimed in any preceding claim, wherein each base station comprises an antenna for receiving/transmitting radio signals, means for deriving an inphase and quadrature phase signal stream from said received signal, means for buffering groups of samples of said inphase and quadrature phase signal steam, covering a period of one symbol for each inphase and quadrature channel, means for performing a fast Fourier transform on the buffered samples, means connected to the fast Fourier transform means, arranged to demultiplex the signals, and a plurality of signal processor means each arranged to handle a particular symbol to apply differential demodulation to each symbol and remove those bits which correspond to differentially demodulating across a frequency hop boundary.
Claim 10
Dependent Claim
36 words
A system as claimed in Claim 9, wherein each signal processor means includes a differential demodulator connected to means for expurgating reference bits, an output of which is connected to a forward error connection coding means.
Claim 11
Dependent Claim
137 words
A system as claimed in Claim 10, wherein each base station is provided with means for providing timing control signals for the mobile terminals, wherein said means includes a Tau Dither control means which is used to control switching means connected between said buffer means and said fast Fourier transform means and operated to determine which output from said buffer means are connected to the fast Fourier transform means, and each signal processing means is arranged to operate upon a modulus of said symbols and either adds or subtracts said modulus from an accumulated value, to provide an output signal which is subjected to a hard limiting process and applied to multiplexing means arranged to multiplex said output signal with output signals from other signal processing means to generate a signal for transmission to the mobile terminals.
References Cited (Backward Citations)
GB2239768A
Cited
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