Pulse or digital communications – Repeaters – Testing
Patent
1994-02-16
1996-01-09
Cangialosi, Salvatore
Pulse or digital communications
Repeaters
Testing
375205, H04B 1713
Patent
active
054835500
DESCRIPTION:
BRIEF SUMMARY
This invention relates to mobile cellular radio systems, and more especially it relates to frequency hopped, code division multiple access, (CDMA) Cellular Radio Systems).
Cellular mobile radio systems require increasing spectrum efficiency, which can be defined in terms of bits per Hz of RF bandwidth over all users in a cell per cell. Recent system concepts based on direct sequence spread spectrum CDMA have demonstrated that increased capacity may be achieved through the effect of `interferer` diversity, wherein every mobile is subject only to the average interference over many users. It has been shown more recently that the use of slow frequency hopped CDMA can, in principle, lead to even higher spectral efficiency through orthogonal hopping, i.e. frequency hopping within a cell wherein the system is adapted to ensure that no two mobile units ever use the same frequency contemporaneously. However, proposals to date have used a form of frequency hopping which requires many bits per hop. This results either in rather poor `interferer` diversity or in long delays. This arises because the time spent on any particular frequency is rather long so that averaging over many frequencies requires a long frame period.
It is an object of the present invention to provide a frequency hopped cellular radio system affording excellent spectrum efficiency and very low delay characteristics.
According to the present invention a frequency hopped cellular mobile radio system, comprises a plurality of base stations each affording a cellular region, or cell, within which communication is facilitated with a plurality of mobile units, each of which mobile units is free to move from cell to cell, the system having in combination the following features; cell into synchronisation, as observed from the base station of that cell, whereby orthogonal frequency hopping between mobile units of the cell is facilitated, frequency hopping between mobile units in different cells being non-orthogonal; maintain communication with a base station selected in dependence upon received signal strength; signal
oise ratio at a base station, whereby transmitted mobile power tends towards the minimum necessary for acceptable communication; to a few bits per hop, the actual number of bits being chosen having regard to performance and overall framing delay constraints; Nyquist filtering of signals effective to constrain interference between hops both in the time domain and in the frequency, domain, hopped dwells being arranged to extend in time beyond a nominal bit transmission period (before and after the period) so as to overlap; quadrature phase shift keyed (QPSK) modulation to de-correlate interference between cells; and,
Preferably the system of error control coding comprises interleaving, whereby adjacent bits are transmitted in different hops and also comprises a forward error correction coding arrangement.
The DPSK modulation is preferably differential binary phase shift keying (DBPSK) with additional randomised QPSK to de-correlate interference between different cells.
The system may include tie feature of power control in a `down-link` wherein the power of transmitted base station signals is controlled in dependence upon the signal
oise ratio of signals received from a mobile unit.
The aforesaid `down-link` power control arrangement may be effected using a spread spectrum pilot which is time division multiplexed with data at a rate of one insertion per hop.
In order to provide for mixed bandwidth services, it is envisaged that some users may be arranged to operate with wider bandwidth hopping, whereby mixed bandwidth services can be provided.
The error control coding may utilise Reed Solomon Coding, which is applied in such a way that one symbol of the Reed Solomon Code corresponds exactly to one hop dwell and as will be appreciated by those skilled in the art, interleaving will not be applied in this case.
According to one contemplated embodiment, a `down-link` receiver, i.e. the receiver at a base station, may be arranged to apply averaging
REFERENCES:
patent: 4189677 (1980-02-01), Cooper et al.
patent: 4355399 (1982-10-01), Timor
patent: 4866710 (1989-09-01), Schaeffer
patent: 5210770 (1993-05-01), Rice
patent: 5216692 (1993-06-01), Ling
patent: 5280537 (1994-01-01), Sugiyama et al.
patent: 5353301 (1994-10-01), Mitzlaff
Cangialosi Salvatore
Roke Manor Research Limited
LandOfFree
Mobile cellular radio systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mobile cellular radio systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mobile cellular radio systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1308089