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PROJECT DESCRIPTION:
The
telecommunication industry has produced an explosion of wireless
technology. The next generation personal communications networks
will need to be able to support a very high level of user traffic
along with a wide range of high quality services at varying bit
rates. However, the ability for wireless channels to achieve high
bit rates at low error rates is severely restricted by multiple
transmission paths with different time delays, attenuation, and
phasors. Current technology utilises multicarrier modulation or
multitone modulation to solve the problem. However, such approaches
often require equalization in the frequency domain, which can prove
to be quite complex with high transmission rates and time-varying
wireless channels. The performance of these systems significantly
degrades if the channel feedback information has error. The
invention relates to multicode transmission, which is a new
technique and can provide reliable high speed transmission of data
over channels that suffer from multipath fading such as in wireless
communications. The incoming high-rate data stream is divided into a
number of parallel low-rate bit streams as in multitone and
multicarrier modulation. The low-rate bit stream using
direct-sequence (DS) spread-spectrum on a single carrier. The choice
of signature sequences or codes are able to separate the
interference between the low-rate bit streams and their multipath
duplicates. Therefore, the ratio of system sensitivity to delay
spread is reduced because of the spreading of the signaling.
Potential Applications: - Wireless local area networks - Wireless
automatic teller machine (ATM) - Wireless video terminals Advantages
over Present Technologies: 1. Robust to fading and multipath
problems without introducing additional equalisation or related
circuitry 2. Reliable 3. Without spreading the original bandwidth of
the transmitted spread spectrum signal |
