摘要:

The performance of symbol-spaced linear and decision feedback (DF) equalisers for a magnetic recording channel with low-pass and matched filter front-ends is investigated. The optimum sampling phases for these two cases is derived analytically, and the timing sensitivity of the equaliser performance is characterised as a function of the recording density. The robustness of receiver performance with respect to target responses belonging to the class of partialresponse channels, as well as the front-end filter shapes, is obtained.

DOI:10.1049/ip-i-2.1993.0026

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The authors propose a bandwidthefficient, asynchronous multiple-access technique with superior probability of error performance. The technique, called waveform division mutipleaccess (WDMA), assigns distinguishable baseband waveforms to the transmitters, and transmissions are asynchronous and occupy the entire available bandwidth. In contrast to direct sequence spread spectrum multiple-access (DS/SSMA), each waveform is continuous over the entire signalling interval. The waveforms are selected to achieve a prescribed multiple-access capability and spectral efficiency. The authors postulate a correlation receiver and select the correlating waveform to minimise a worst case average error probability for each receiver, given the transmit waveforms. The requirements of the waveforms are formulated in the context of constrained optimisation. Plots are presented of typical waveforms, spectra, autocorrelation and partial cross-correlation functions. Also presented are error probability curves for noncoherent differential phase shift keying (DPSK) operating in a Gaussian environment. These results indicate that WDMA is a viable alternative to DS/SSMA in applications where bandwidth is scarce and strict security is of no concern. Potential applications are transmission of public safety (police, fire, medical etc.), utility and distress informations.

DOI:10.1049/ip-i-2.1993.0027

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Because of the random properties of practical communication networks the unique decoding of CCMA codes should include two steps. First, to identify the current system state, and secondly to uniquely decode the added codewords. When no special information is provided to distinguish different system states, the conventionally defined CCMA codes in most previous studies will be no longer uniquely decodable. Based on this consideration, the concept of system state-independent-uniquedecodable (SIUD) CCMA codes is introduced. A construction method of SIUD CCMA codes and the corresponding performance evaluation are also presented.

DOI:10.1049/ip-i-2.1993.0028

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Reed-Solomon decoders can be designed using time or frequency domain algorithms. The main advantage of the time domain method is its regular computational structure, an attractive feature for a flexible VLSI implementation. The main disadvantage of this is the relatively high computation count, hence it is important to find means of reducing the computational complexity of the time domain method. Several modifications to the time domain Reed-Solomon decoding algorithm are described for reducing its computational complexity by about 60%, as well as regular VLSI architectures for implementing the time domain algorithm. The paper concludes with a discussion of the advantages and disadvantages of the time domain decoding technique.

DOI:10.1049/ip-i-2.1993.0029

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A multiple access protocol for transmitting time-constrained packets on bus networks is presented. Based on carrier sense multiple access/ collision detection (CSMA/CD) protocol, a new protocol is developed and its performance evaluated by computer simulation. An approximate analysis model for this protocol is also presented. Numerical results indicate that the new protocol achieves a better performance, and the approximate analysis model is also effective.

DOI:10.1049/ip-i-2.1993.0030

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The authors present a new approach for estimating the impulse response of indoor radio channels using the signal subspace concept. The technique is based on the use of information theoretic criteria, a high-resolution spectral analysis technique, and principal component analysis. It is shown that the new technique can be used to overcome difficulties experienced by conventional methods and, as a result, can produce more accurate estimates of the channel parameters. The use of this technique is demonstrated by data analysis using both simulated and measured indoor radio channel data.

DOI:10.1049/ip-i-2.1993.0031

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A coherent optical CDMA network employing Gold sequences for the encoding operation is analysed, and its performance is evaluated in the presence of shot noise and employing the exact distribution for the interfering components. Spreading and despreading are performed directly in the optical domain by means of a lithium niobate Mach-Zehnder phase modulator. BPSK and OOK modulation formats are considered. The results obtained show that the system can be profitably employed without requiring synchronisation between the stations

DOI:10.1049/ip-i-2.1993.0032

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Architectures for optical TDM switching with low control complexity, which would be suitable for implementation with lithium niobate switches and fibre delay lines, are discussed. The networks are mathematically equivalent to strictsense nonblocking Cantor networks, and use the same control algorithm. The penalty paid for low control complexity is a large number of components. All such networks use ‘feed-forward’ delay lines which provide superior crosstalk performance and more uniform attenuation than existing designs. Architectures, both with and without frame integrity, are considered; performance is characterised in terms of attenuation and crosstalk.

DOI:10.1049/ip-i-2.1993.0033

出版商:IEE    

年代:1993

数据来源: IET