Jonghyun Park

Capacity analysis for distributed antenna systems using cooperative transmission schemes in fading channels

Wireless systems equipped with distributed antennas can provide enhanced data throughput as well as improved signal quality when appropriate cooperative transmission schemes among antennas are employed. In this paper, the performance of distributed antenna systems (DAS) under the influence of Rayleigh fading and log-normal shadowing effects is investigated for different cooperation strategies, and corresponding statistical distributions for both the signal-to-interference ratio (SIR) and the capacity are presented. Specifically, the ergodic capacity per remote antenna (RA) is determined when n RAs cooperatively transmit the desired signal to the target receiver, which is compared with the non-cooperative single-antenna transmission (SAT) case. Using the results, a preferable mode of operation for given geographic locations of the receiver is determined. We further propose to perform an adaptive operation between the cooperative and non-cooperative modes under the capacity maximization criteria, and quantify exact amounts of capacity gain over individual transmission modes.

Precoder and Capacity Expressions for Optimal Two-User MIMO Transmission with Per-Antenna Power Constraints

In this letter, multiuser multiple-input multiple-output (MIMO) precoding which achieves the Gaussian broadcast channel (GBC) capacity under the per-antenna power constraint (PAPC) is investigated. In particular, closed-form expressions for both the MIMO precoder and the corresponding sum capacity are presented for the two-user case. We show that the result can also be utilized to provide the two-user capacity expression under the total power constraint (TPC) of transmit antennas.

Implementation of DSP-based digital receiver for the SDR application

In recent times, the demodulator structure is reconfigurable for the SDR (software defined radio) technology that supports various communication reception modes in the radio communication. Owing to the SDR technology, it is possible to work in several modes without the peripheral hardware. We implement the M-ary FSK and BPSK demodulators on the DSP (TMS320C6203) board without the conventional complex analog circuits. We also propose a synchronization algorithm for BPSK demodulation. We also find out the demodulated signal after emulating the source program by graph view window of the DSP development tool, i.e. code builder. Based on the results, we can get the same performance by using the DSP technique as compared with the conventional complex circuit. It is confirmed that the programmed DSP can demodulate the various kinds of modulation signal by software programming.

Performance of distributed MISO systems using cooperative transmission with antenna selection

Performance of downlink transmission strategies exploiting cooperative transmit diversity is investigated for distributed multiple-input single-output (MISO) systems, for which geographically distributed remote antennas (RA) in a cell can either communicate with distinct mobile stations (MS) or cooperate for a common MS. Statistical characteristics in terms of the signal-to-interference-plus-noise ratio (SINR) and the achievable capacity are analyzed for both cooperative and non-cooperative transmission schemes, and the preferred mode of operation for given channel conditions is presented using the analysis result. In particular, we determine an exact amount of the maximum achievable gain in capacity when RAs for signal transmission are selected based on the instantaneous channel condition, by deriving a general expression for the SINR of such antenna selection based transmission. For important special cases of selecting a single RA for non-cooperative transmission and selecting two RAs for cooperative transmission among three RAs surrounding the MS, closed-form formulas are presented for the SINR and capacity distributions.

Capacity and outage performance of regional signal combining using distributed antennas

For cellular systems with base stations (BSs) equipped with distributed antennas, various cooperative signal transmission strategies can be employed. In this paper, we analyze the trade-off between the transmission capacity and the outage probability when downlink signals from two geographically separated antennas are combined. It is demonstrated a significant reduction in the outage probability can be achieved while simultaneously improving the capacity, when signal combining is selectively performed based on the carrier-to-interference ratio (CIR) measurement at a given mobile station (MS). Experimental results show the outage (CIR less than 0 dB) probability reduces by 54.1% with the capacity increase of 7.4% for the fading channel condition.

Channel Norm-Based Power Control in Downlink Multi-User Distributed MIMO Systems

We consider distributed multiple-input multiple-output systems with remote antennas (RA) connected to the base station via high-capacity backhaul, which are operated under the per-antenna power constraint (PAPC). We propose a simple strategy to determie transmission power for each user, referred to as channel norm-based power control (NBPC) to obtain near-optimal performance in terms of the sum-rate maximization and the log-sum-rate maximization for fairness improvement, applicable to any number of RAs and users. In particular, a closed-form solution to maximize the sum-rate using the NBPC is presented. We also show that the proposed strategy used in conjunction with existing multi-user transmission schemes derived under the total power constraint can be efficiently applied to systems under the PAPC.

Derivation of the Maximum Capacity Using the Jacobian Transformation Method for Systems Employing Adaptive Cooperation

The performance of cooperative transmission in wireless systems depends on the maximum signal quality from multiple transmission sources. The knowledge of the probabilistic distribution for the maximum statistics, therefore, plays an important role in determining the system performance. Obtaining the distribution in many cases relies on experimental results, especially when random variables of interest are mutually correlated. In this paper, we provide a derivation method for the maximum distribution using the Jacobian transformation rule, and investigate the performance of systems employing adaptive cooperation among remote antennas. A closed-form expression of the maximum achievable capacity is derived and verified by computer simulation.