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Interference between femto-cell systems is a critical factor for the deployment of such systems in, e.g., residential areas. In this paper we report on a residential channel measurement campaign focusing on the channel properties for femto-cell systems. We characterize basic channel properties such as delay spread and interference levels between different furnished residential houses. In addition...
Orthogonal frequency division multiplexing (OFDM) systems may confront significant intercarrier interference (ICI) when applied in doubly selective channels. Furthermore, the insufficient cyclic prefix (CP) leads to interblock interference (IBI) which again results in ICI. These interferences cause an early error floor in conventional receivers. In this paper, we characterize the doubly selective...
This paper provides an overview of the design of transmit and receive beamformers and transmit power allocation for MIMO relays. Soft and hard methods for interference cancelation are presented, which play a critical role for all MIMO relays whether they are full-duplex or half-duplex, regenerative or non-regenerative, one-way relay or two-way relay. A perspective of MIMO relays in a network of many...
Multi-input multi-output (MIMO) is an attractive solution to high data rate underwater acoustic communications (UAC) with limited bandwidth. However, the long delay spread characteristic of UAC channels makes the equalization challenging for those MIMO schemes. Although maximum likelihood sequence estimation (MLSE) is known to be optimum and is intensively used in many terrestrial wireless applications,...
Limited feedback beamforming improves link reliability with a small amount of feedback from the receiver to the transmitter. The performance of such a closed loop MIMO system is unknown in interference limited cellular environments, when the base stations have limited or no coordination. This paper establishes the degradation in throughput due to uncoordinated other cell interference and delay on...
The different propagation times due to the distinct distance between the BSs and MSs result in inter-cell asynchronous interference, which severely destroy system performance. How to mitigate inter-cell asynchronous interference by making use of SLNR precoding is the key to this paper. Firstly, a framework of Cooperative Base Station Systems (Co-BS) was developed and the delay between the cells was...
In this paper, we investigate the performance of superimposed training-based channel estimation techniques considering an asynchronous code-division multiple-access (CDMA) uplink transmission over frequency-selective fading channels. In that, we analyze the performance of a channel estimation and data detection scheme based on superimposed training for space-time spreading (STS) systems. Our results...
In this paper we quantify 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8 downlink system performance for a macro cell hexagonal grid scenario. The system performance is analyzed for a closed loop Single User Multi-Input Multi Output (SU-MIMO) mode and compared with Single Input Multiple Output (SIMO) and Multi-User (MU) MIMO modes, for a full buffer scenario and static...
This paper investigates the impact of delayed channel state information at the transmitter (CSIT) on the MIMO broadcast channel with block diagonalization (BD) preceding. First, an upper bound for the achievable throughput is provided, which shows that BD is more robust to imperfect CSIT than zero-forcing precoding as it has fewer inter-user interfering streams. Due to residual inter-user interference,...
The combined use of orthogonal frequency-division multiplexing (OFDM) and wireless multiple-input multiple-output (MIMO) links is becoming common. For many applications, such as ad hoc wireless networks, interference is a significant issue. MIMO links allow for the spatial mitigation of interference; however, spatial interference mitigation when using OFDM modulation performs somewhat poorly because...
Similar to its frequency division duplex (FDD) counterpart, there is currently great interest in introducing multiple-input multiple-output (MIMO) antenna technique into time division-synchronized code division multiple access (TD-SCDMA) high-speed packet access evolution (HSPA+) system within 3GPP. To this end, per-antenna rate control (PARC), selective-PARC (S-PARC) and dual-stream transmit antenna...
Cooperative communication enables nodes to share their antennas to form a virtual multiple-input multiple-output system and achieve spatial diversity gain. A multi-packet reception protocol, based on cooperative communication and network-assisted diversity multiple access, is proposed to employ multiple receive antennas to separate the collided packets quickly and provide the multi-packet reception...
Recently, attention on wireless communications has been shifted from multiple-input multiple-output (MIMO) systems to multiuser MIMO (MU-MIMO) systems, which serve several users simultaneously in frequency and time. For a system with multiantenna users, block diagonalization (BD) is a technique, where multiuser interference can be completely canceled. For realizing the BD algorithm, the base station...
In the multiple-input multiple-output (MIMO) broadcast channel with imperfect channel state information (CSI), neither the capacity nor the optimal transmission technique have been fully discovered. In this paper, we derive achievable ergodic rates for a multi-antenna fading broadcast channel when CSI at the transmitter (CSIT) is delayed and quantized. It is shown that not all possible users should...
We consider the optimization of transmit powers and linear receivers for transmission from multiple single-antenna terminals to a central receiver equipped with multiple antennas and aim to minimize the overall transmission power with respect to given targets on the signal-to-interference-and-noise-ratio. This design goal has been previously investigated with respect to frequency flat channels, which...
An orthogonal frequency division multiplexing (OFDM) system suffers performance degradation when the length of the cyclic prefix (CP) is less than the channel impulse response. The root cause of this degradation is the inter-carrier interference (ICI) and inter-symbol interference (ISI) introduced by the excessive multipath delay. Generally, MIMO beamforming is helpful in mitigating such interference...
In this paper, a tap-wise LMMSE channel estimator for MIMO W-CDMA is derived. Descrambling operations applied to delayed versions of the received signal whiten the input signal. The descrambling process thus breaks up the full channel autocorrelation matrix (including spatial and temporal correlation) into several independent, small autocorrelation matrices that include only spatial correlation. The...
In the paper, performance of multiuser multiple-input multiple-output eigenbeam-space division multiplexing (E-SDM) systems in the downlink transmission is evaluated in both uncorrelated and correlated time-varying fading environments based on computer-generated data. In the ideal case, using the block diagonalization (BD) scheme, inter-user interference can be completely eliminated at each user;...
Channel adaptive transmission in multi-user MIMO systems is seen as a promising concept to achieve high spectral efficiencies in future radio networks: Based on feedback on actual channel conditions, the base station allocates transmission resources to the user terminals where they can support high data rates. However, due to the delay between evaluation of the channels at the terminals and application...
In this paper, we consider channel shortening for cyclic-prefixed block transmission system over multiple input multiple output (MIMO) channels. A time domain equalizer (TEQ) is necessary at the receiver front head to mitigate intersymbol interference (ISI). Melsa, Younce, and Rohrs (1996) proposed the most popular MSSNR channel shortening method for single input single output (SISO) channels based...
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