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This paper presents a new linear programming approach for throughput maximization on the uplink of a multiclass variable spreading gain code-division multiple-access (CDMA) multicellular system in Rayleigh fading for both binary phase-shift keying (BPSK) and quaternary phase-shift keying (QPSK) modulations. Based on the improved Gaussian approximation technique, we derive exact closed-form expressions of the outage probability, which are used as a physical (PHY) layer constraint of the maximization problem. We show that it is possible to transform the nonlinear constraint into a set of equivalent linear expressions. This facilitates the formulation of a new linear throughput maximization that noticeably requires less computational complexity than the known nonlinear approaches. Furthermore, due to the simplicity of the linear approach, we can include the constraints of such higher layers, i.e., media access control (MAC) and call admission control (CAC) layers, into the proposed formula. Accordingly, we introduce two linear programming optimization formulas. One is for MAC-PHY optimization, and another is for cross-layer optimal CAC policy. In the case of MAC-PHY optimization, the throughput is maximized, at low background noise level, when every user retains the same bit energy, particularly in the case where the difference in data rates is high. Nonetheless, at high levels of background noise, the throughput would be maximized when a larger amount of bit energy is allocated to the high-rate users. For the joint optimal policy, the throughput and the blocking probability are optimized and improved up to 50% in comparison to those of the conventional CAC policy, which is known as the complete sharing policy. Index Terms--Code division multiaccess, fading channels, interference, land mobile radio cellular systems, linear programming.

A new exact explicit expression is derived for the ergodic capacity of maximal ratio combining (MRC) schemes over arbitrarily correlated Rician fading channels. This is used to study the effects of channel correlation on the ergodic capacity. Numerical results reveal that both the phase and the magnitude of correlation have an impact on the ergodic capacity of Rician fading channels. This is in contrast to correlated Rayleigh fading, where the phase of the correlation has no effect on the ergodic capacity. It is also observed that negatively correlated branches in Rician fading may lead to an increase in ergodic capacity beyond that obtained by uncorrelated branches. Index Terms--Channel capacity, maximal ratio combining (MRC), Rician fading, correlated fading, wireless SIMO systems.

This paper presents a unified analytical method for computing the average E [g ([[summation]].sup.K.sub.k=1] [y.sub.k] + b)) (b))J of some arbitrary function g(.) when x is a gamma random variable and independent of the arbitrary random variables [y.sub.1], [y.sub.2], ..., [y.sub.K]. This leads to new explicit expressions for the averages of some specific functions including, erfc([square root of z]), exp(-z), [z.sup.n], and ln(1 + z), in terms of the moment generating functions of [y.sub.1], [y.sub.2], ..., [y.sub.K]. Index Terms--Cochannel interference, fading channels.

This paper presents a new analytical performance analysis of slow frequency-hopped synchronous spread-spectrum multiple-access (FHSS-MA) networks employing nonorthogonal binary frequency-shift keying (BFSK) and having arbitrary spacing between the hopping carriers. Taking into account the crosstalk due to the nonorthogonality of both hopping carriers and BFSK tones, and based on an accurate interference analysis, we derive new expressions for the average probability of error of a reference signal subjected to a number of similar signals in the additive white Gaussian noise Rayleigh-faded channel. These are used to investigate the effect of carrier and tone spacing on the spectral efficiency of an FHSS-MA network. It is shown that the spectral efficiency depends primarily on the shape of the employed pulses, in addition to both carrier and tone spacing. Numerical results show that rectangular pulses give higher spectral efficiency as compared with the half-sine pulses. Furthermore, orthogonal tone spacing is shown to be more efficient in the case of rectangular pulses, whereas half-sine pulses become more efficient with the nonorthogonal signaling. Index Terms--Frequency-hop (FH) communication, frequency-shift keying (FSK), interference, multiaccess communication, spread spectrum communication.

We present new packet-error rate (PER) analysis for both slotted and unslotted direct-sequence spread-spectrum packet communication systems in a slow Rayleigh fading environment. Based on the accurate improved Ganssian approximation, we derive closed-form expressions for the cumulative probability distribution function of the signal-to-interference-plus-noise ratio in binary phase-shift keying (PSK), quadratic PSK, and differential PSK-based code-division multiple-access (CDMA) systems having different types of chip waveforms including bandwidth-efficient waveforms. This leads to new accurate unified expressions for the PERs that account for bit-to-bit error dependence, which are valid for packets with unequal power levels. These new results facilitate accurate computation of the throughput performance of CDMA-based ALOHA local radio networks. Index Terms--Multiple-access (MA) communications, packet communication systems, Rayleigh fading channels, spread spectrum communications.

We derive a new closed-form expression for the exact bit error probability for the detection of a non-coherent binary phase shift keying signal experiencing a multiple co-channel asynchronous interferers in nonselective Rayleigh-fading channels. The analysis accounts for the effect of timing offset of the different interfering signals as well as the correlation between two adjacent bit intervals. It is valid for general wave-shaping pulses and allows interfering signals to have unequal power levels. The results are used to assess the accuracy of the Gaussian interference approximation for diversity receivers. Index Terms-Co-channel interference, digital communication systems, diversity reception, fading channels.

This correspondence is concerned with the statistical dependence of hits due to multiple-access interference in the time-unslotted frequency-hopping (FH) packet networks. Relying on the technique of joint probability generating functions (PGFs), we give a formal proof that if the ratio of the number of interfering packets to the number of frequency slots K/q is held constant, hits due to multiple-access interference are asymptotically independent as q [right arrow] [infinity]. We also derive expressions for the correlation coefficients of hits in the packet. Index Terms--Frequency hopping (FH), packet code-division multiple access (CDMA), packet radio networks, spread-spectrum communication systems, unslotted multiple access.

This letter is concerned with the interference analysis in time-unslotted frequency-hopping code-division multiple-access packet networks with error control coding. We derive, under the conditional independence assumption, a new exact closed-form expression for the packet error probability of a reference packet in the presence of other K interfering packets. In contrast to the previously known results, the computational complexity of the new result is independent of K. We also develop a new tight upper bound on packet error probability relying on mapping the unslotted system into an equivalent slotted one experiencing the same level of short-term average interference. The accuracy of the proposed approximation is demonstrated by some numerical examples and is shown to be tighter than the previously used results. Index Terms--Frequency hopping, packet code-division multiple-access (CDMA), unslotted multiple access.