Error performance of vertical-BLAST over Rayleigh and Nakagami fading channels

The study of statistical distribution of errors is a prerequisite in the design of appropriate coding techniques to effectively control errors. An architecture, V-BLAST, that promises very high spectral efficiency is analyzed and compared for two transmitter-receiver arrangements. We analyzed the system performance over Rayleigh and Nakagami channels along with statistical analysis of errors. Average error burst lengths, average error tree lengths and BER are determined. We also evaluate the effects of different interleaver depths. It is shown that increasing the number of transmitters and receivers, and uncorrelated channel paths give improved performance

Mobile radio channel impulse response: measurements and interpretations

An impulse response measurement campaign was undertaken at 1.8 GHz in Hong Kong. This paper presents a selection of measurement results. A pseudorandom sequence clocked at 30 MHz occupying an RF bandwidth of 60 MHz was used as a probing signal. The results taken at a selected location are analyzed for CIR parameters like delay spread, average delay and significant number of paths. An attempt has been made to relate the measured data to the geometry of environmental features surrounding the transmitter and the receiver

Mobile radio channel impulse response: measurements and interpretations

An impulse response measurement campaign was undertaken at 1.8 GHz in Hong Kong. This paper presents a selection of measurement results. A pseudorandom sequence clocked at 30 MHz occupying an RF bandwidth of 60 MHz was used as a probing signal. The results taken at a selected location are analyzed for CIR parameters like delay spread, average delay and significant number of paths. An attempt has been made to relate the measured data to the geometry of environmental features surrounding the transmitter and the receiver

Error performance of vertical-BLAST over Rayleigh and Nakagami fading channels

The study of statistical distribution of errors is a prerequisite in the design of appropriate coding techniques to effectively control errors. An architecture, V-BLAST, that promises very high spectral efficiency is analyzed and compared for two transmitter-receiver arrangements. We analyzed the system performance over Rayleigh and Nakagami channels along with statistical analysis of errors. Average error burst lengths, average error tree lengths and BER are determined. We also evaluate the effects of different interleaver depths. It is shown that increasing the number of transmitters and receivers, and uncorrelated channel paths give improved performance

Uplink channel estimation for IMT-DS system

The IMT-DS system is one of the approved 3G radio interface standards which employ RAKE receivers to exploit multipath diversity. This paper discusses a new dimension in DS-CDMA channel estimation, i.e., chip-level adaptive channel estimation. A novel despreader-respreader based channel estimator (DRCE) is proposed to obtain uplink (UL) channel estimates at chip-level which resolves the deficiencies of conventional methods that work at symbol level. The DRCE employs an adaptive filter whose weights are adapted by using an LMS algorithm. The performance of the RAKE receiver with DRCE for an IMT-DS system is evaluated in terms of BER by simulations for pedestrian and vehicular channel

Uplink channel estimation for IMT-DS system

The IMT-DS system is one of the approved 3G radio interface standards which employ RAKE receivers to exploit multipath diversity. This paper discusses a new dimension in DS-CDMA channel estimation, i.e., chip-level adaptive channel estimation. A novel despreader-respreader based channel estimator (DRCE) is proposed to obtain uplink (UL) channel estimates at chip-level which resolves the deficiencies of conventional methods that work at symbol level. The DRCE employs an adaptive filter whose weights are adapted by using an LMS algorithm. The performance of the RAKE receiver with DRCE for an IMT-DS system is evaluated in terms of BER by simulations for pedestrian and vehicular channel

Downlink channel estimation for IMT-DS

IMT-DS system is an approved terrestrial radio interface standard for 3G mobile communication based on direct sequence code division multiple access (DS-CDMA). It employs a RAKE receiver to exploit multipath diversity. This paper discusses a new dimension in DS-CDMA channel estimation i.e., chip-level adaptive channel estimation. The DL channel of an IMT-DS system consists of time-multiplexed pilot and data symbols to facilitate coherent detection. To obtain channel estimates during pilot symbols, we propose a chip level adaptive channel estimation which performs better than the conventional method. For slow fading channels, like a pedestrian channel, zero order interpolation provides satisfactory performance. However, for fast fading channels, a common decision directed algorithm is applied whose performance is limited due to error propagation. The proposed schemes are assessed over the IMT-DS system by performing simulation

Effect of doppler frequency on pilot arrangements in wireless OFDM systems

With the rapid growth of wireless communications in recent years, the need for high speed data transmission is increased. OFDM is a promising candidate for achieving high data rates in mobile environment due its resistance to ISI, which is a common problem found in high speed data communication. Channel Estimation for wireless OFDM systems requires transmission of pilot tones. The success of channel estimate at a desired BER and Doppler frequency is highly dependent on how the pilot signals are arranged. This paper describes in detail the effect of Doppler frequency on different pilot arrangements in Wireless OFDM systems, under Rayleigh Faded channel conditions. This paper also addresses the issue, of how to arrange the location of pilot tones, and propose a new pilot insertion scheme and compare it with existing schemes. It is shown, that for lower Doppler frequencies the proposed scheme performs better than other existing pilot schemes. It is also shown here via simulations that over Rayleigh faded channels it is more efficient to use fewer pilot tones in all symbols, instead of using all tones as pilot tones in some symbols. We also compare existing schemes on different Doppler frequencies, one that uses some tones as pilot tones in each symbol (comb) than a scheme that uses all tones as pilot tones in some symbols (block). In comb arrangement one would form an instantaneous estimate of the channel impulse response in each symbol, and use it to update average channel estimate in some fashion. In block arrangement, where one periodically uses all the tones in a symbol as pilot tones, i.e. periodically one entire symbol would be used just to transmit training data, and channel estimate would be obtained from this