Receive Antenna Diversity Research Articles

Field Measurements of a Hybrid DVB-SH Single Frequency Network With an Inclined Satellite Orbit

Field measurements of a DVB-SH network with both satellite and terrestrial transmitters are presented. The system is a Single Frequency Network transmitting video streams to vehicular terminals with up to 4 branches of receiver antenna diversity. The signal is transmitted in the S-band at 2.1859 GHz with both time and frequency synchronization of the terrestrial repeaters with the satellite's signal. The time and frequency variations are cancelled out at the satellite gateway, but because these can not be canceled at all locations, and because the satellite's position in space is variable (in an inclined orbit) the terrestrial repeaters are made to cancel the residual time and frequency variation. The field measurements include data taken in late 2008 through 2009 with multiple repeaters located in several cities including Las Vegas, NV, Raleigh and Durham, NC, as well as various morphologies, and with elevation angles to the satellite ranging from 25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> to 52 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . This paper presents coverage data for these various morphologies, modulation and code rates, as well as various MPE-iFEC interleaver settings used to ameliorate the effects of long shadowed intervals such as when the vehicle goes under highways or bridges where there signal is obscured for several seconds. We observed excellent performance in hybrid mode with better than 99% of the measured seconds error free. In satellite-only mode, the MPE-iFEC interleaver raised the performance from 81% to 91% averaged over all environments, including dense urban.

Performance of Receive Diversity UWB Systems with Pulse Amplitude and Position Modulation

In this paper, we extend ultra-wideband (UWB) single input single output (SISO) systems with a hybrid pulse amplitude and position modulation (PAPM) to single input multiple output (SIMO) systems using receive antenna diversity. The performance of a rake receive diversity combining scheme for UWB SIMO systems with a PAPM is examined in a log-normal multipath fading channel and also compared with that of a time-switched transmit diversity (TSTD) multiple input single output (MISO) system. It is seen that as the number of receive antennas increases, the receive diversity combining system improves the error performance. It is shown that the TSTD UWB MISO systems offer the performance equivalent to the receive diversity combining scheme for SIMO systems.

MRC in the Presence of Asynchronous Cochannel Interference Over Frequency-Selective Rayleigh Fading Channels

This paper studies the performance of Rake receivers with maximal ratio combining (MRC) in the presence of cochannel interference over slowly varying frequency-selective fading channels with combined spatial receive antenna diversity and temporal multipath diversity. Two models for the instantaneous powers of the residual multipath components and the resolved cochannel interfering signals, which represent the overall interfering signals, are employed. The first model considers the phase asynchronism between the desired signal replicas and interfering signals, whereas the second model assumes that the instantaneous powers of interfering signals incoherently add up. The desired signal replicas and interfering signals are assumed to experience statistically independent Rayleigh fading processes with arbitrary statistics. For the system model previously described, new closed-form expressions for the probability density function (pdf) of the combined signal-to-interference-plus-noise ratio (SINR) are derived. These expressions are then used to obtain formulas for various performance measures. The case study under consideration and the corresponding derived expressions for the statistical measures generalize many previous results and can usefully be employed to investigate the impact of various system and channel parameters on the performance of Rake receivers with MRC in the presence of cochannel interference.

Experimental Evaluation of Time Diversity Effect in Hybrid ARQ Considering Space and Path Diversity for Downlink OFDM-Based Broadband Radio Access

This paper presents experimental evaluations of the effect of time diversity obtained by hybrid automatic repeat request (HARQ) with soft combining in space and path diversity schemes on orthogonal frequency division multiplexing (OFDM)-based packet radio access in a downlink broadband multipath fading channel. The effect of HARQ is analyzed through laboratory experiments employing fading simulators and field experiments conducted in downtown Yokosuka near Tokyo. After confirming the validity of experimental results based on numerical analysis of the time diversity gain in HARQ, we show by the experimental results that, for a fixed modulation and channel coding scheme (MCS), time diversity obtained by HARQ is effective in reducing the required received signal-to-interference plus noise power ratio (SINR) according to an increase in the number of transmissions, K, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity using a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain obtained by time diversity is almost saturated at the maximum number of transmissions in HARQ, K' = 4 in Chase combining and K' = 2 in Incremental redundancy, since the improvement in the residual packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the initial packet transmission arising from appropriately selecting the optimum MCS in AMC. However, the experimental results elucidate that the time diversity in HARQ with soft combining associated with antenna diversity reception is effective in improving the throughput even in a broadband multipath channel with sufficient path diversity.

The Implementation of a 2/4/8 Antennas Configurable Diversity OFDM Receiver for Mobile HDTV Application

Two pre-FFT adaptive array (AA) antenna combiners and a post-FFT carrier diversity (CD) combiner are integrated with a Japan Terrestrial digital TV (ISDB-T) OFDM receiver using 90 nm 7M1P CMOS process. A 2/4/8-antenna diversity receiver can be configured and a low-cost 4 antenna diversity reception system can be realized in one LSI by making use of the AA-CD two-stage diversity combining method. Mobile reception performance is increased by 1.63 times using a denoise filter circuit and SPLINE interpolator under urban 6-path Rayleigh fading (TU6) model with 2-antenna post-FFT carrier diversity (2CD) combing mode. The die area is 49 and the power consumption is 310 mW.

Uplink multiservice capacity and interference statistics of WCDMA macrocells with antenna diversity reception in a multipath fading environment

We generalize the interference modeling method developed by Romero-Jerez et al. to include the effect of the number of Rake fingers, uplink orthogonality factor, number of receiving antennas and the cell radius on the cell uplink capacity. With this model, the capacity of the system for voice only users, data users only and mixed services is obtained. It is noticed that increasing the cell radius from 400 to 800 m reduces the uplink capacity for voice and data services. It is shown that the synchronous WCDMA will increase the uplink capacity by 16.9%. For the nonfading case, the uplink capacity is 12.5% higher than the uplink capacity with a fading channel.

Frequency-Domain QR-Decomposed and Equalized MLD for Single-Carrier MIMO Systems over Multipath Fading Channels

This letter describes a new QR-decomposition maximum likelihood detector that is combined with frequency-domain equalization for single-carrier transmission based multiple-input multiple-output systems. By utilizing the equalized substreams to adjust the frequency selectivity in corresponding substreams in subsequent stages, the packet error rate performances of the proposed detector is superior to that of the minimum mean squared error receiver by a factor of the receive antenna diversity gain.

DS-CDMA Downlink Site Diversity with Frequency-Domain Equalization and Antenna Diversity Reception

The use of frequency-domain equalization based on minimum mean square error criterion (called MMSE-FDE) can significantly improve the bit error rate (BER) performance of DS-CDMA signal transmission compared to the well-known coherent rake combining. However, in a DS-CDMA cellular system, as a mobile user moves away from a base station and approaches the cell edge, the received signal power gets weaker and the interference from other cells becomes stronger, thereby degrading the transmission performance. To improve the transmission performance of a user close to the cell edge, the well-known site diversity can be used in conjunction with FDE. In this paper, we consider DS-CDMA downlink site diversity with FDE. The MMSE site diversity combining weight is theoretically derived for joint FDE and antenna diversity reception and the downlink capacity is evaluated by computer simulation. It is shown that the larger downlink capacity can be achieved with FDE than with coherent rake combining. It is also shown that the DS-CDMA downlink capacity is almost the same as MC-CDMA downlink capacity.

Carrier Frequency Synchronization and Tracking for OFDM Systems with Receive Antenna Diversity

Blind carrier frequency synchronization for orthogonal frequency division multiplexing (OFDM) systems with receive diversity is proposed in this paper. This method utilizes the fact that different receive branches contain uncorrelated observations about the same information bits. Due to receive diversity, our synchronizer can perform well without virtual subcarriers when channel state information (CSI) is known. In addition, we shall analyze the effects of CSI errors on the carrier frequency offset (CFO) estimation and show that the proposed algorithm is robust to CSI error. In particular, we derive the Cramer-Rao bound (CRB) from the mean square error (MSE) of the carrier frequency synchronizer. Computer simulation results show the performance improvement of our synchronizer to the single antenna systems and to the existing method.

Theoretical Analysis of Decision Directed Block Iterative Channel Estimation for OFDM Mobile Radio

Orthogonal frequency division multiplexing (OFDM) is one of the promising transmission techniques for next generation mobile communication systems. Accurate channel estimation is essential for coherent OFDM signal transmission. So far, many pilot-assisted channel estimation schemes have been proposed. In the case of packet transmission, each received packet can be repeatedly processed by decision feedback to improve the channel estimation accuracy, resulting in a decision directed block iterative channel estimation (DD-BICE). However, decision feedback of erroneously detected data symbols degrades the packet error rate (PER) or bit error rate (BER) performance. In this paper, theoretical analysis is presented for the DD-BICE taking into account the decision feedback errors assuming quadrature phase shift keying (QPSK) data modulation. A 2-dimensional (2D) averaging filter is used for reducing the negative impact of decision feedback errors. The impacts of 2D averaging filter and antenna diversity reception are discussed and the validity of the theoretical analysis is confirmed by computer simulation.

Potential of CDMA450 for rural network connectivity

This article evaluates CDMA450 as a potential solution for rural data and voice connectivity. We begin by analyzing the main strengths of CDMA450, but also some of the potential limitations for rural coverage, from both a technical and an economic standpoint. We argue that CDMA450 is a promising technology, competitive in both capacity-centric urban environments and in coverage-centric rural environments. Consequently, we discuss the opportunities of providing universal coverage by adopting a business model targeting both urban and rural deployments, and utilizing urban to rural cross-subsidization. We then explore the advantages of deploying CDMA450 using a fixed wireless (WLL) model. To this end, we explore the effective range of WLL CDMA450, and the impact of using directional antennas and receive antenna diversity in real-world commercial CDMA450 deployment in Romania. If used properly, these techniques can aid us in increasing cell radii and thus lead to substantial cost benefits

Exact closed-form symbol error rate of arbitrary rectangular M-QAM over Rayleigh fading for two-branch transmit diversity

By using a pre-averaging method, we successfully derive an exact closed-form symbol error rate (SER) expression for the particular case of two transmit-one receive antenna diversity system employin...

Joint Frequency-Domain STTD and Antenna Diversity Reception Based on MMSE Criterion for OFDM/TDM

In this letter, we introduce frequency-domain space-time transmit diversity (STTD) encoding/decoding to orthogonal frequency division multiplexing combined with time division multiplexing (OFDM/TDM) on a frame-by-frame basis (i.e., over several concatenated OFDM signals in the frequency-domain) to achieve both spatial and frequency diversity gains and improve the bit error rate (BER) performance. The theoretical BER performance is evaluated by numerical computation using the derived conditional BER and confirmed by computer simulation.

The Effect of Imperfect Channel Estimation on the Performance of Maximum Ratio Combining in the Presence of Cochannel Interference

In this paper, the effects of imperfect channel estimation on maximum ratio combining performance in receive antenna diversity systems with multiple cochannel interferers are examined. The channel considered is a slowly varying flat Rayleigh fading channel that is also spatially independent. The combiner weights are the imperfect estimates of the desired user's fading coefficients and are assumed to be complex Gaussian distributed. Closed-form expressions for signal-to-interference-plus-noise ratio distribution and outage probability are obtained for both equal-power and unequal-power interferer scenarios. Using these expressions, the effect of channel estimation quality on system performance is investigated

Exact closed‐form symbol error rate of arbitrary rectangular M‐QAM over Rayleigh fading for two‐branch transmit diversity

AbstractBy using a ‘pre‐averaging method’, we successfully derive an exact closed‐form symbol error rate (SER) expression for the particular case of two transmit‐one receive antenna diversity system employing arbitrary rectangular M‐QAM signalling over flat Rayleigh fading. Fading between branches are assumed independent. Both identical and distinct branch powers are considered. The closed‐form SER obtained is in terms of elemental functions containing no unevaluated integrals nor lengthy and complicated transcendental functions. Simulation results show that square M‐QAM outperforms rectangular M‐QAM for a given size M. Monte Carlo simulation results are found in excellent agreements with theoretical results. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Investigation of STBC and TSTD Transmitter Diversity Effect Using Chase Combining in Spread OFDM Broadband Packet Wireless Access

This letter investigates the effects of the Space-Time Block Code (STBC) transmitter diversity and Time Switched Transmitter Diversity (TSTD) schemes while simultaneously considering the time diversity effect derived from Chase combining and the frequency diversity effect for downlink Spread OFDM packet wireless access in a broadband multipath fading channel. The simulation results show that when pilot channel based channel estimation is performed, TSTD improves the required average received signal energy per symbol-to-noise power spectrum density ratio by approximately 1.0 and 0.5 dB compared to one-branch transmission, without and with antenna diversity reception, respectively, while the benefit of STBC is small due to channel estimation error, when the maximum number of retransmissions in Chase combining is three in a 12-path Rayleigh fading channel with the root mean squared delay spread of 0.3 μsec and the maximum Doppler frequency of 20 Hz.

Adaptive Coded Modulation With Receive Antenna Diversity and Imperfect Channel Knowledge at Receiver and Transmitter

Unifying and generalizing the works of Cai and Giannakis and Oien et al., the performance of an adaptive trellis-coded modulation system where receive antenna diversity is implemented by means of maximum ratio combining is analyzed and optimized. As in the work of Cai and Giannakis, the analysis is done in the presence of both estimation and prediction errors. Rayleigh fading on each subchannel is considered, with the estimation and prediction being performed independently on each subchannel. The system optimization process is done in such a way that the throughput is maximized under a bit-error-rate (BER) constraint. The numerical example employs a Jakes-fading spectrum and shows how the power should be distributed between pilot and data symbols and how often pilot symbols should be transmitted for maximum throughput under an instantaneous (with respect to the predicted channel) BER constraint.

Maximum achievable diversity order for cascaded Rayleigh fading channels

In this Letter, we investigate the error rate performance of coherent M-ary phase shift keying (M-PSK) modulation over cascaded Rayleigh fading with receive antenna diversity. Through the derived symbol error rate (SER) expression, we present the maximum diversity order achievable over such channels and demonstrate the performance degredation in comparison to conventional Rayleigh channels.

Outage capacity improvements in multicellular CDMA systems using receive antenna diversity and fast power control

In this paper, we analyze the uplink outage capacity improvements in multicellular code-division multiple-access systems using receive antenna diversity and fast power control schemes that can track multipath fading. The channel is modeled as slowly varying Rayleigh fading with lognormal shadowing and path loss. Closed-form expressions are obtained for the outage capacity of the system by approximating the total intracell and intercell interference distributions. We show that by controlling the power level of a user at the output of the diversity combiner and imposing the condition that a user does not transmit when in a deep fade, the average intercell interference level of the system is significantly reduced. As a result of this reduction, we demonstrate both analytically and through simulations that the outage capacity of the system is improved more than linearly with increasing number of antenna elements.

Cancellation Moderating Factor Control for DS-CDMA Non-linear Interference Canceller with Antenna Diversity Reception

In a CDMA non-linear interference canceller, a generated replica of an interference signal is multiplied by a positive number smaller than unity, which is called cancellation moderating factor (CMF), to prevent interference enhancement due to inaccurate replica subtraction. In this paper, two CMF controlling schemes applicable to a multistage parallel interference canceller with multi-antenna (spatial diversity) reception are proposed. They control CMF by using the mean square error of the complex channel gain or by using the ratio of the estimated power of each interference signal to remaining interference signals' power, in order to mitigate the replica subtraction error due to inaccurate channel estimation. The performance of the proposed schemes are evaluated by computer simulations assuming an asynchronous uplink single chip-rate variable spreading factor DS-CDMA system. The simulation results show that the proposed schemes with higher order diversity reception improve the bit error rate (BER) performance compared with a conventional scheme considering the tentative decision error or fixed CMF settings. Their performance improvement is by 0.1--0.9 dB in terms of the required Eb/N0 at an average BER of 10-5 over exponentially decaying 5-path Rayleigh distributed channels when the number of receiving antennas is 6.