| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥3,000,000 (Direct Cost: ¥3,000,000)
|
|---|
| Research Abstract |
A data exchange system enabling to deal with various kinds of information is proposed for the road informatics. Fast-frequency Hopped Spread Spectrum(SS) communication system with CPM-DD (Differential Detection) is applied for the purpose of free access to the system and efficient power use of the hand-held equipment. Asynchronous system access is preferable to a load communication application, then system performance in the multi-user environment must be clarified.Thus, this reserch will be pursuied to clarify that how many users are able to communicate simultaneously under the condition that the applied type of code sequence and available hopping-frequency number are given, Results are obtained through computer simulation. An additive white Gaussian noise channel and the Rayleigh fading channel with the maximum Doppler frequency of up to 200 Hz are assumed for the propagation channel, which simulates a moving terminal on a car running the motor- way with up to 100 Km/h. Rayleigh fading is the worst case assumption for the road information application in the case no line-of-sight path opened.
To track the differential detector with a hopped frequency in the fading environment is very difficult because a phase of the received signal is affected by random variation from a multipath phenominon. Prediction of a channel characteristics is a powerful countermeasure for that purpose, and then we emply RLS-MLSE(Recursive Least Squares- Maxmum Likelihood Sequence Estimation) assited by Viterbi decoding algorithm. Block coding modulation technique is also used for an improvement of the BER characterisitcs. From the above coerced techniques, we could attain tracking ability of the differential detector up to 200 Hz of the maximum doppler frequency : i.e., we can achieve BER of l0^<-4> under the two-path frequency selective fading channel model with D/U=0 dB.Furthermore, when we give 52 chip-hops, 23 simultaneous users could communicate each other with BER of 10^<-2>.
|
