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In this letter, we compare the capacity of a massive multiple-input multiple-output (MIMO) system using a low-resolution analog-to-digital converter (ADC) and a linear detector against a conventional MIMO system with higher order modulation and near maximum likelihood (ML) detection. We show that in the low-signal-to-noise ratio (SNR) regime, the quantized massive MIMO system can outperform the conventional large MIMO system; however, for high SNR, the conventional MIMO system with a near ML detector can outperform the extreme 1-bit quantized massive MIMO system. An analytical framework that derives the achievable rate of a linear minimum mean-squared error (MMSE)-based detector in a massive MIMO configuration, with the assumptions that the front-end is limited to a low-resolution ADC and channel estimation is imperfect, is presented.

An efficient high order multi-user multiple-input multiple-output (MU-MIMO) subspace detector is proposed. The detector employs joint modulation classification (MC) and subspace detection (SD), by which the modulation type of the interferer is estimated, while multiple decoupled streams are individually detected. The algorithmic contributions are on two levels. First, the preprocessing channel matrix decomposition overhead is reduced, using special layer ordering followed by permutation-robust QR Decomposition and elementary matrix operations. Second, a hierarchical MC scheme is proposed, comprising feature-based and near-optimal likelihood-based classifiers, as well as a classifier that always assumes the interfering modulation type to be a fixed high order quadrature amplitude modulation. An efficient hardware architecture that realizes the proposed algorithms is presented. Simulations demonstrate that depending on the channel condition, one of the proposed schemes can achieve near interference-aware performance with a minimum complexity overhead.

One of the challenging tasks in LTE baseband receiver design is synchronization, which determines the symbol boundary and transmitted frame start-time, and performs cell identification. Conventional algorithms are based on correlation methods that involve a large number of multiplications and thus lead to high receiver hardware complexity and power consumption. In this paper, a hardware-efficient synchronization algorithm for frame timing based on K-means clustering schemes is proposed. The algorithm reduces the complexity of the primary synchronization signal for LTE from 24 complex-multiplications, currently best known in the literature, to just 8. Simulation results demonstrate that the proposed algorithm has negligible performance degradation with reduced complexity relative to conventional techniques., Comment: IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, 2016

A highly efficient receiver architecture for intraband contiguous carrier aggregation (CA) is described. The downconversion architecture is done in two stages; the first stage is done in the analog domain using a direct-conversion receiver, whereas the second stage is done in the digital domain using offset frequency digital mixing to separate the carriers. The novelty in the architecture stems from its ability to compensate for the different carrier frequency offsets (CFOs) between the two transmitted carriers, and unlike traditional approaches, the receiver uses a single complex digital mixer for baseband carrier separation. The receiver architecture also compensates for in-phase and quadrature gain and phase imbalance (IQI) inherent in direct-conversion receivers. It is shown that, in our new architecture, IQI compensation can be done post the digital mixer, thus enabling a low-power implementation to this impairment.

In this paper, we study the uplink achievable rate by a massive multiple-input multiple-output (MIMO) system in which the base station is equipped with a large number of 1-bit analog-to-digital converters (ADCs). We propose a linear minimum mean-squared error (MMSE)-based detector that accounts for the non-linearity effects of the 1-bit quantization as well as for channel estimation error. An analytical framework that derives the achievable rate of the MMSE-based detector in a massive MIMO configuration under the assumption of 1-bit quantized ADCs and channel estimation error is presented. We compare the achievable rates of a massive MIMO system using a 1-bit ADC and a linear detector against a conventional MIMO system with higher-order modulation and near maximum likelihood (ML) detection. We show that in the low signal-to-noise ratio (SNR) regime with channel estimation error, the quantized massive MIMO system can outperform the conventional large MIMO system; however for high SNR, the conventional MIMO system with a near ML detector can outperform the quantized massive MIMO system.

This paper presents an optimized low-complexity and high-throughput multiple-input multiple-output (MIMO) signal detector core for detecting spatially-multiplexed data streams. The core architecture supports various layer configurations up to 4, while achieving near-optimal performance, as well as configurable modulation constellations up to 256-QAM on each layer. The core is capable of operating as a soft-input soft-output log-likelihood ratio (LLR) MIMO detector which can be used in the context of iterative detection and decoding. High area-efficiency is achieved via algorithmic and architectural optimizations performed at two levels. First, distance computations and slicing operations for an optimal 2-layer maximum a posteriori (MAP) MIMO detector are optimized to eliminate the use of multipliers and reduce the overhead of slicing in the presence of soft-input LLRs. We show that distances can be easily computed using elementary addition operations, while optimal slicing is done via efficient comparisons with soft decision boundaries, resulting in a simple feed-forward pipelined architecture. Second, to support more layers, an efficient channel decomposition scheme is presented that reduces the detection of multiple layers into multiple 2-layer detection subproblems, which map onto the 2-layer core with a slight modification using a distance accumulation stage and a post-LLR processing stage. Various architectures are accordingly developed to achieve a desired detection throughput and run-time reconfigurability by time-multiplexing of one or more component cores. The proposed core is applied as well to design an optimal multi-user MIMO detector for LTE. The core occupies an area of 1.58MGE and achieves a throughput of 733 Mbps for 256-QAM when synthesized in 90 nm CMOS.

New expressions for the soft decision bit log-likelihood ratio (LLR) of a MIMO system using quadrature amplitude modulation (QAM) taking into account channel estimation error (CEE). The bit LLR for the maximum likelihood (ML) and the linear minimum mean-squared error (MMSE) receivers are derived, showing in both receivers explicit scaling of the LLR that is a function of the QAM symbol and the CEE variance. These new expressions for the LLRs are used to show that only modest improvements in the link performance are achieved relative to the LLRs that do not take into account the CEE. This indicates that separating the detector design from channel estimation does not significantly impact the system performance, which leads to simplifications in the overall receiver implementation.

Linear decoding of space–frequency block codes (SFBCs) based on the Alamouti structure with orthogonal frequency-division multiplexing (OFDM) requires the channel to be constant across two consecutive tones. However, time-dispersive multipath fading channels exhibit frequency-selective behavior wherein the channel across two tones will vary. This paper provides analytical tools for evaluating the performance of SFBCs with OFDM in frequency-selective channels. The analysis uses the average signal-to-interference-plus-noise ratio (SINR) as a sufficient statistic to describe the performance of SFBCs in frequency-selective channels. A unified formula is derived to characterize the channel correlation between two consecutive tones for various frequency-selective channels. A closed-form solution of the average SINR is obtained, which takes into account imperfect channel estimation and frequency selectivity. An interpolation method of the channel estimate is proposed, which is shown to improve the bit-error-rate performance by 3 dB at a high SNR. The accuracy of the theoretical analyses is verified by numerical simulations under multipath channels such as the International Telecommunications Union (ITU) pedestrian and vehicular models.

In Part I, we presented algorithmic optimizations for a soft-output (SO) tree-search MIMO detector targeted at reducing the node count complexity for a given error-rate performance. We present in this part the architecture for a hardware-efficient pipelined detector that incorporates all these optimizations. A detailed gate complexity analysis of the architecture is conducted, including arithmetic optimizations to minimize the use of multipliers for distance computations by exploiting the lattice structure, as well as efficient pointer logic for implementing child enumeration, internal node-pruning and node-skipping steps. For multitone OFDM symbol detection using multiple tree-search detectors, we propose an efficient scheduling scheme that exploits the slack in node count from tone-to-tone detection. By ordering the tones according to increasing order of their channel matrix orthogonality defect, the detector maximizes the slack of early terminating detectors and forwards it to ill-conditioned tones that require more detection time. Case studies and simulation experiments were conducted based on a 4-layer 64-QAM MIMO system for LTE. Simulations and VLSI synthesis results demonstrate that the proposed optimizations require a chip area of only 85 kGE to implement a 64-QAM SO MIMO detector for LTE capable of attaining almost ML performance with an SNR loss of only 0.85 dB.

Optimum soft-output (SO) multiple-input multiple- output (MIMO) tree-search detection algorithms pose significant implementation challenges due to their nondeterministic processing throughput and high computational complexity. In this two-part work, we present extensive algorithmic and architectural optimizations of the sphere-decoding algorithm targeted at achieving practical tradeoffs between desired link performance and affordable computational complexity. The algorithmic optimizations in this part span the tree-search traversal scheme, leaf processing step, internal node-pruning and skipping step, child enumeration based on a state-machine, adaptive radius scaling for LLR clipping, QR-decomposition based on minimum cumulative residuals, and multitree configurations. The optimizations demonstrate that a 64-QAM SO MIMO detector for LTE is capable of attaining almost ML performance with an SNR loss of only 0.85 dB at 1% BLER by visiting at most 200 tree nodes.

A family of architecture-aware Raptor codes is constructed. The proposed construction scheme is targeted to design rate-compatible structured codes that span a wide range of rates and block sizes while still having hardware-efficient decoder implementations. The codes match the corresponding fixed-rate LDPC codes in error-correcting performance, decoding convergence speed, and message-memory requirements. Three novel steps are incorporated in the scheme: 1) a new group-based design of the code source matrix; 2) an architecture-aware row splitting-after-merging technique to construct irregular precodes; and 3) structured LT row-encoding. A code instance was designed accordingly and compared to standardized LDPC codes. The error-rate performance closely matches that of LDPC, whereas the convergence speed and message count gaps are narrowed down to values between [1.1x, 1.8x] and [1.1x, 1.3x], respectively.

We propose a novel approach for data-aided estimation of the mixer gain and phase imbalances in the analog front-end of direct-conversion receivers. We estimate the inphase and quadrature imbalance (IQI) parameters isolated from the fading channel estimate and use the estimated IQI parameters for time-domain compensation. The motivation behind this approach is the scenario where the training symbols used for IQI estimation are transmitted from different antenna ports than those used for data transmission. In this scenario, the conventional composite IQI and channel estimate cannot be used for signal detection because the training and data symbols experience different channels. An example of this scenario is the long-term evolution (LTE) standard where the synchronization and broadcast signals are transmitted from different antenna ports than those used for data transmission. Numerical results show that our approach achieves up to 10 dB improvement using only two training symbols.

In this paper, dual-layer multi-user multiple-input multiple-output systems are studied. Building on the low-complexity layered orthogonal lattice detector (LC-LORD), an efficient sub-optimal joint modulation classification (MC) of the co-scheduled user and data detection receiver is developed. By adjusting the Max-Log-Maximum-a-Posteriori MC approach to the limitations of LC-LORD, and expanding it to include distances of counter maximum likelihood hypothesis symbols, the decision metric for MC is shown to be an accumulation over a set of tones of Euclidean distance computations also used by the LC-LORD detector for bit log-likelihood ratio soft decision generation. Simulations demonstrate that with a small complexity overhead, the proposed approaches achieve near interference-aware performance. An efficient hardware implementation scheme is presented.

Optimum data detection schemes for dual layer multi-user multiple-input multiple-output (MU-MIMO) systems are studied. A joint maximum likelihood (ML) modulation classification (MC) of the co-scheduled user and data detection receiver is developed. By expanding the max-log-maximum-a-posteriori MC approach to include distances of counter ML hypothesis symbols, the decision metric for MC is shown to be an accumulation over a set of tones of Euclidean distance computations also used by the ML detector for bit log-likelihood ratio soft decision generation. With a small complexity overhead, the proposed approach achieves near-optimal performance. An efficient hardware architecture is presented for the proposed approach.

The methodology used to evaluate the performance of the various MIMO schemes in orthogonal frequency division multiplexing (OFDM) WiMAXWiMAX stands for Worldwide Interoperability for Microwave Access. systems is described. The per-tone signal-to-noise plus interference ratio (SINR) of a MIMO OFDM system is derived in a multi user, multicell and multisector communication system. The sector average spectral efficiency for a coded MIMO OFDM system is evaluated under a single frequency reuse deployment scenario. It is shown that the second antenna at the subscriber station receiver provides significant gains over single transmit single receive antenna (SISO) systems. The rate 2 spatial multiplexing MIMO scheme on the downlink improves the sector spectral efficiency by 10% over single transmit and two receive antenna (SIMO) system in a single frequency reuse deployment. It is also shown that in a time-division duplex (TDD) WiMAX system, the gain in downlink spectral efficiency from beamforming can be very large if the delay between the uplink channel estimate and the downlink beamforming is small compared to the coherence time of the channel. On the uplink, it is shown that the collaborative spatial multiplexing increases the spectral efficiency by 9% over a SIMO system with the same number of receive antennas at the base station (BS). Significant gains in uplink spectral efficiency are seen with more antennas at the BS and by using uplink beamforming as compared to SISO.

In this paper, dual-layer multiple-input multiple-output (2 × 2 MIMO) systems that use 1024-QAM constellations are studied. Using the layered orthogonal lattice detector (LORD) algorithm, which achieves optimal maximum-likelihood (ML) performance at the expense of high complexity, we argue that the low-complexity version of LORD (LC-LORD) introduces a significant performance degradation, especially with high channel correlation. We propose several approaches that outperform LC-LORD at a lower complexity. These approaches are based on improving the location of a reduced region of search within a 1024-QAM constellation, as well as optimizing the bit log likelihood ratio (LLR) approximation. The proposed approaches were studied in the context of non-iterative and iterative detection and decoding, and significant gains were achieved in both cases.

The problem of optimal likelihood based modulation classification (MC) for optimal detection in 2×2 multiuser MIMO (MU-MIMO) receivers is considered. The optimal Log-MAP classifier is computationally exhaustive, and its sub-optimal Max-Log-MAP version poses remarkable degradation in performance. Between these two extremes, we propose four computationally efficient methods for MC, by taking special subset constellation points for Euclidean distance computations that constitute the decision metric. Compared to the Max-Log-MAP classifier, the proposed schemes achieved a frame error rate (FER) gain of 0.5dB with uncorrelated channels, while the gains reach 2dB under highly correlated channel conditions.

This paper develops an estimation algorithm for the time and amplitude of arrival of a known transmitted sequence over a single-path fading channel. The algorithm is optimized to enhance robustness to fast channel fading and low signal-to-noise ratio (SNR) conditions, which are common in wireless location applications. The paper also presents a noise and fading bias correction technique for amplitude of arrival estimation that improves the estimation accuracy significantly. The proposed algorithm is then applied to the case of code-division multiple-access (CDMA) wireless location finding for which the paper gives simulation results that demonstrate significant estimation accuracy improvement over known algorithms.

We present novel soft-input soft-output (SISO) multiple-input multiple-output (MIMO) detectors based on the Chase detection principle [1] in the context of iterative and decoding (IDD). The proposed detector complexity is linear in the signal modulation constellation size and the number of spatial streams. Two variants of the SISO detector are developed, referred to as SISO B-Chase and SISO L-Chase. An efficient method is presented that uses the decoder output to modulate the signal constellation decision boundaries inside the detector leading to the SISO detector architecture. The performance of these detectors significantly improves with just a few number of IDD iterations. The effect of transmit and receive antenna correlation is simulated. For the high-correlation case, the superiority of SISO B-Chase over the SISO L-Chase is demonstrated., 5 pages, 3 figures

A dual-layer multiple-input multiple-output (MIMO) system with multi-level modulation is considered. A computationally efficient soft-input soft-output receiver based on the exact max-log maximum a posteriori (max-log-MAP) principle is presented in the context of iterative detection and decoding. We show that the computational complexity of our exact max-log-MAP solution grows linearly with the constellation size and is, furthermore, less than that of the best known methods of Turbo-LORD that only provide approximate solutions. Using decoder feedback to change the decision thresholds of the constellation symbols, we show that the exhaustive search operation boils down to a simple slicing operation. For various simulation parameters, we verify that our solution performs identically to the brute-force exhaustive search max-log MAP solution., 4 pages, 3 figures

We consider a multi-user multiple-input multiple-output (MU-MIMO) system that uses orthogonal frequency division multiplexing (OFDM). Several receivers are developed for data detection, where the receivers have partial state information about the MU-MIMO transmission; however, the modulation constellation of the co-scheduled users is unknown. We propose a joint data detection and maximum likelihood (ML) modulation classification (MC) of the co-scheduled user. We show that the decision metric for MC is an accumulation of the Euclidean distances used by the ML single-user MIMO detector. An efficient hardware architecture emerges that exploits this commonality between the classification and detection steps and results in sharing of hardware resources.

The performance of a DS/CDMA system using M-ary orthogonal modulation with noncoherent demodulation is evaluated. The system operates in a multipath fading channel. A RAKE receiver structure with equal gain combining is used for demodulation. An approximation to the bit error probability is given which depends only on the first- and second-order moments of the multipath energies. The analysis results are compared with the results from computer simulations. It is seen that the approximation is accurate for multipath energies with realistic coefficient of variation. The system performance is also evaluated in terms of the capacity, which is defined as the number of users that can be supported at a given bit error probability. The approximation is used to evaluate the capacity reductions due to power variations caused by multipath fading. >

Transmitting signals over multipath fading channels causes distortions and variations at the receiver. For narrow-band signals, the envelope of the received signal is well characterized by a Rayleigh random process. Rayleigh fading causes large variations in the signal envelope. For wide-band signals, the effect of Rayleigh fading is mitigated. The paper considers the effect of receiver processing on the mitigation effect for wide-band DS/CDMA signals. The mitigation effect is shown by a reduction of the coefficient of variation of the received power as a function of bandwidth spreading. The parameters chip rate, processing gain, and the number of multipath components tracked are investigated for their effect upon the mitigation-the mitigation effect is sensitive to combinations of these parameters. >

A log-max generalized bit log-likelihood ratio (GLLR) was derived in an earlier work of Wang et al. for soft decision decoding of quadrature amplitude modulation that takes into account channel estimation error. The results in the above paper show that the GLLR metric outperforms the conventional LLR metric that does not account for channel estimation error. In trying to reproduce the results of the above paper, our simulations indicate that their results were obtained without proper scaling of the transmit constellation. Conversely, through simulations, we demonstrate that by properly scaling the constellation to have unity average energy, the GLLR metric does not result in a noticeable advantage in the bit error rate over the conventional LLR metric for practically meaningful values of the channel estimation error.

We examine the statistical distribution of received power when a subscriber terminal with multiple transmit antennas beamforms on the uplink of a wireless orthogonal frequency-division multiplexing system to a basestation with multiple receive antennas. We assume that a time-division duplex terminal has incomplete uplink channel knowledge obtained by measuring the downlink channel during basestation transmissions. The basestation transmissions employ cyclic delay diversity, of which the terminal is unaware. The distribution of uplink power received at the basestation, with and without downlink cyclic delay diversity and with various types of power constraints at the terminal, allow us to make some surprising conclusions about how the power constraints and cyclic delay influence the performance of beamforming. We show that beamforming gains need to be examined critically beyond simple average performance metrics to conclude that they are superior to simpler channel-unaware methods. We also conclude that cyclic delay on the downlink is very beneficial to beamforming on the uplink, even with restrictive types of power constraints.

Since multi-antenna (MIMO) systems are becoming more popular thanks to their inherent potential for capacity improvement, interference from MIMO transceivers is an increasingly serious concern. Spatial multiplexing schemes are particularly vulnerable to multi-user interference. Fortunately, this interference can be mitigated, when the channel matrices show a sufficient spatial separation. In this paper, we quantify the separability of multi-user MIMO channels using actual measurements in a scenario where a single outdoor base station transmits to two indoor mobile receivers. To quantify the spatial distance between the two users, we compare the spatial correlation matrices using two simple measures: (i) matrix collinearity, and (ii) the condition number ratio. Both measures are directly linked to MIMO system performance. Our measurement-based evaluations demonstrate that the downlink channels of different users can have a significantly different spatial structure, even when the users are in the same room. This leads to the following conclusions: (i) new multi-user MIMO models are needed to describe the spatial characteristics of different users, and (ii) spatial interference can be well managed by appropriate scheduling and precoding algorithms.

In this paper, we show that the use of cyclic delay diversity (CDD) on the downlink (DL) can improve the performance of uplink (UL) diversity methods such as antenna selection in a time-division duplexing (TDD) system. An analytical framework for showing why CDD transmission on the DL improves UL diversity transmission in TDD system is provided. The analysis is used to quantify the gain in the UL received signal-to-noise ratio (SNR) when DL CDD is used. The analytical results show that for a 2times2 MIMO system that uses DL CDD, UL transmit diversity based on antenna selection improves the average UL SNR by 0.41 dB relative to the case when CDD is not being applied at the BS transmitter and improves the 1% CDF UL SNR by 1.58 dB. Measurement-based analysis validates the analytical results using measured frequency response of a MIMO system using a wideband channel sounder.

The system architecture of the cellular base station modem engine (CBME) is described. The CBME is a single-chip multichannel transceiver capable of processing and demodulating signals from multiple users simultaneously. It is optimized to process different classes of code-division multiple-access (CDMA) signals. The paper will show that through key functional system partitioning, tightly coupled small digital signal processing cores, and time-sliced reuse architecture, CBME is able to achieve a high degree of algorithmic flexibility while maintaining efficiency. The paper will also highlight the implementation and verification aspects of the CBME chip design. In this paper, wideband CDMA is used as an example to demonstrate the architecture concept.

With the deadline for wireless E911 looming, and the drive for location enhanced services increasing, a method for locating phones in a IS-95 CDMA network is needed. To address the phase II FCC requirement of locating a wireless E911 caller within a radius of 125 meters, 67 percent of the time, one method employing the following techniques: time of arrival (TOA), time difference of arrival (TDOA), and an amplitude difference based angle of arrival (AD-AOA) from a network perspective is examined. The paper discusses an initial investigation of the proposed method via simulation and results obtained. The investigation methodology is as follows: define a searcher for simulation and sensitivity analysis, simulate performance of the receiver from captured field data, and simulate a system for location prediction performance using readily available channel models.

The link performance of transmit diversity (TD) schemes for third generation CDMA systems is analyzed. Orthogonal transmit diversity (OTD) and space-time transmit diversity (STTD) are compared. It is shown that the link performances of OTD and STTD are nearly the same. However, STTD requires additional receiver processing, and STTD is not directly extendable to more than 2 antennas, because rate one space-time block codes do not exist for greater than 2 antennas. Also, an interleaving approach is shown that works for various TD schemes as well as non-TD.

For narrowband signals the envelope of the received signal is well characterised by a Rayleigh random process. Rayleigh fading causes large variations in the signal envelope. For wideband signals, the effect of Rayleigh fading is mitigated. This paper considers the effect of receiver processing on the mitigation effect for wideband DS/CDMA signals. The mitigation effect is shown here by a reduction of the coefficient of variation of the received power as a function of bandwidth spreading. The parameters chip rate, processing gain and the number of multipath components tracked are investigated for their effect upon the mitigation-the mitigation effect is sensitive to combinations of these parameters. >

In order to deal with the service demand of a mixture of high and low mobility users a system with overlapped macrocells and microcells has been proposed. In this paper we present architectures for code division multiple access (CDMA) based hybrid macrocell/microcell systems. These architectures are based on the principle of reducing the interference to macrocell users in a highly dense environment. This is accomplished by replacing the macrocell antenna with many microcell antennas, which are connected to a macrocell processor. The functions of this processor is to configure the proper connections between users and antennas. The characteristics of microcell propagation are used to justify the proposed antenna connection protocols which include 2-antenna and 3-antenna protocols. System architectures for both linear and two-dimensional service areas are discussed. System performance is evaluated in terms of carrier-to-interference ratio (CIR). The analysis procedure models the number of users in each cell as a Poisson distributed random variable. The CIR expressions for both the conventional and hybrid systems are reformulated. It is shown that the proposed architecture can lead to a dramatic increase in capacity as compared to conventional CDMA cellular systems. >

Mobile radio fading analyses typically assume a single frequency carrier transmitted through the propagation medium. The results are then used for the case of narrowband transmission. New phenomena occur with wideband transmission. This paper presents an analysis of the mitigation of the Rayleigh fading effect for wideband direct sequence code division multiple access (DS/CDMA) signaling. There are measurements that show this phenomenon. The reduction of the Rayleigh fading effect is an advantage of CDMA over narrowband transmission systems and it eases the burden of CDMA power control. A general expression for the coefficient of variation of the received wideband signal power is derived. It is shown how the coefficient of variation of the received power decreases as the bandwidth spreading increases. This paper also analyzes the time correlation needed for other analyses (e.g., CDMA power control). >

Packet reservation multiple access (PRMA) allows a group of spatially dispersed terminals to transmit packet voice and data over a common channel. A means to model and evaluate the effects of packet transmission errors on PRMA is developed. PRMA is considered in the context of a cellular system, and the effects of fading on the performance of PRMA are studied. PRMA performance is assessed in terms of system capacity, outage, and cellular efficiency when the transmission channel is subject to slow and fast fading. It is shown that for fast-fading channels simple forward-error correction is sufficient for acceptable system performance. In slow-fading channels, however, other techniques such as selection diversity are required. >

This paper presents an analysis of the CDMA forward link capacity and coverage in a multipath fading channel for slow moving users. Previous analysis of CDMA capacity ignored several factors that affect the forward link performance. The analysis presented in this paper takes into account short term fading, lognormal shadowing, frame error rate (FER) requirement, outage, power allocation, soft handoff, the number of multipaths and the number of required RAKE fingers. Finally, both Rayleigh and Rician fading are considered.

The overall throughout and delay performance of the 1XTREME proposal in 3GPP2 and the HSDPA proposal in 3GPP are provided. The performance sensitivity to call model, peak data rate, hybrid ARQ, C/I feedback delay, and multipath interference is examined using a quasistatic system simulator. In all cases, performance is bounded using two simple scheduling approaches, maximum C/I and round robin.

A high data rate proposal for a 1.25 MHz DS-CDMA system, called 1XTREME (1xEV-DV), is capable of supporting peak rates of up to 4.8 Mbps and average data rates of approximately 1 Mbps. It is a true evolution of the cdma-2000 CDMA system, being fully backward compatible and therefore able to support both voice and data users on the same carrier. A new forward shared channel (F-SHCH) with an associated forward control channel carries the high-speed packet data. The associated forward control channel structure is shown to offer a 30% increase in the active users on the system over a typical structure. Furthermore, additional channels are added in the reverse link to support the various throughput-enhancing features of 1XTREME. In this paper, the details of the air-interface are presented along with the description of each channel. Also, the simulated performance of the F-SCH and the forward control channels are presented.

A key requirement for next generation CDMA systems is to provide a high bit rate packet data service and improved sector throughput for both low and high mobility applications. A 1.25 MHz DS-CDMA evolution called 1XTREME (Third Generation Enhanced Modulation and Encoding) has been proposed. 1XTREME uses a forward shared channel (F-SHCH) that is shared by multiple packet data users and is capable of supporting peak rates of up to 5 Mbps, compared to third generation CDMA system indoor peak data rates of 460 kbps and 2 Mbps for IS-2000 and W-CDMA, respectively. In this paper the link performance of the F-SHCH is evaluated for different modulation and coding scheme (MCS) configurations. Based on the link results, the average sector throughput is presented for two simple scheduling algorithms, as well as performance as a function of the maximum allowed FER operating point.

Wireless location finding is gaining considerable attention in the field of wireless communications. This is due to a recent USA government mandate for wireless service providers to locate users in emergency situations within a high precision. In this paper, we introduce a new estimation scheme for the time and amplitude of arrival of a code division multiple access signal transmitted over a single-path Rayleigh fading channel for location finding applications. Optimum choices of the estimation scheme parameters are derived. The paper also presents a new noise and fading bias equalization technique for amplitude of arrival estimation that enhances its estimation precision significantly. The paper gives simulation and field trial results that show significant robustness of the proposed scheme to high noise levels and fast channel fading.

The performance of the forward link for an IS-95 based CDMA system in case of slowly moving mobiles in a flat Rayleigh fading channel is evaluated. It is shown that soft handoff improves the system capacity at the expense of an increase in the hardware requirements at the cell site. The analysis shows the interaction between the design parameters and their effect on system performance. Outage, blocking and coverage probabilities are defined and used to characterize system performance.