This paper proposes a new adaptive Interference Cancelling Equalizer (ICE) with a blind algorithm. From a received signal, ICE not only eliminates inter-symbol interference, but also cancels co-channel interference. Blind ICE can operate well even if training signals for the interference are unknown. First, training signal conditions for applying blind ICE are considered. Next, a theoretical derivation for blind ICE is developed in detail by applying the maximum likelihood estimation theory. It is shown that RLS-MLSE with diversity, which is derived for mobile radio equalizers, is also effective for blind ICE. Computer simulations demonstrate the 40kb/s QDPSK transmission performance of Blind ICE as a blind canceller with two branch diversity reception under Rayleigh fading in a single interference environment. The simulations assume synchronous training; the canceller is trained for the desired signal but not for the interference signals. Blind ICE can be successfully achieved at more than -10dB CIR values when average Eb/N0 is 15dB and a maximum Doppler frequency is 40Hz.

A receiving system suitable for multipath fading channels with co-channel interference is described. This system is equipped with both an M-sectored directional antenna and an adaptive equalizer to mitigate the influence due to multipath propagation and co-channel interference. By using directional antennas, this receiving system can separate desirable signals from undesirable signals, such as multipath signals with longer delay time and co-channel interference. It accepts multipath signals which can be equalized by maximum likelihood sequence estimation, and rejects both multipath signals with longer delay time and co-channel interference. Based on computer simulation results, the performance of the proposed receiving system is analyzed assuming simple propagation models with Rayleigh-distributed multipath signals and co-channel interference.

This paper proposes M-ary/SSMA using co-channel interference cancellation techniques and presents comparisons with conventional DS/SSMA and other systems. First, ideal models of DS/SSMA and M-ary/SSMA using co-channel interference cancellation techniques are analyzed. In the cancellation circuit of DS/SSMA, when an error bit of other user's data arises, the received signal is degraded by "voltage addition" of the error sequence. While, in M-ary/SSMA, it is degraded by only "power addition" of the error code. Therefore, though the circuits are complicated, bit error rate of the proposed system can be improved considerably. Further, improvement of spectral efficiency in these systems are shown for several bit error rate and chip waveforms.

We propose a direct-sequence spread-spectrum multi-access (DS/SSMA) receiver that incorporates multipath diversity combining and multistage co-channel interference (CCI) cancellation. This receiver structure which is more resistant to the near/far problem essentially removes more and more of the CCI with each successive cancellation stage. With the assumption that perfect channel estimates have been obtained, we analyze the bit error rate (BER) performance of this system when received powers are unequal. Results show that the BER can approach that of a single-user case as the number of CCI cancellation stages increases.

This paper analyzes the performance of the capacity controlled digital radio system, which controls the number of modulation levels according to the amount of traffic. These analyses are performed under thermal noise and co-channel interference. As a result, the throughput improvement is approximately 16 times comparing with the fixed capacity system which has the designed outage probability of 0.1%. Theoretical results are applied to the future mobile communication system which utilizes TDMA access method or burst co-dec, and it is found that the reuse distance can be improved to 1/5 times when the designed outage probability is 0.1%.

It is difficult for a receiver in Asynchronous SSMA systems to eliminate co-channel interference, when the receiver doesn't know the sequence of the co-channel interference. In this paper, a filter for eliminating co-channel interference without using the knowledge of the sequence of co-channel interference in an asynchronous SSMA system, in which each transmitter/receiver is assigned an infinite number of sequences and select a sequence secretly for information security. The filter gathers the co-channel interference energy into some puleses and scatters the signal energy widely. The receiver can clip the co-channel interference energy by losing small amount of signal energy. This is a new solution for the near-far problem in an asynchronous SSMA system using secret sequences.