Output and delay process analysis for slotted CDMA wirelesscommunication networks with integrated voice/data transmission

This paper presents the output and delay process analysis of integrated voice/data slotted code division multiple access (CDMA) network systems with random access protocol for packet radio communications. The system model consists of a finite number of users, and each user can be a source of both voice traffic and data traffic. The allocation of codes to voice calls is given priority over that to data packets, while an admission control, which restricts the maximum number of codes available to voice sources, is considered for voice traffic so as not to monopolize the resource. Such codes allocated exclusively to voice calls are called voice codes. In addition, the system monitoring can distinguish between silent and talkspurt periods of voice sources, so that users with data packets can use the voice codes for transmission if the voice sources are silent. A discrete-time Markov process is used to model the system operation, and an exact analysis is presented to derive the moment generating functions of the probability distributions for packet departures of both voice and data traffic and for the data packet delay. For some cases with different numbers of voice codes, numerical results display the correlation coefficient of the voice and data packet departures and the coefficient of variation of the data packet delay as well as average performance measures, such as the throughput, the average delay of data packets, and the average blocking probability of voice calls     

MIMO slotted ALOHA systems with collision resolution and truncated HARQ transmission and combining

In this paper, we investigate throughput and delay enhancement for two multi-user multiple-input multiple-output (MIMO) systems one with space-time block coding (STBC), the other with spatial multiplexing (SM) at the transmitter. Users operate using the slotted ALOHA (SA) protocol to access the wireless channel resulting in a high probability of collision. For both systems, we consider the uplink scenario, and we propose to recover the collided packets with spatial successive interference cancelation (SSIC) and a protocol for retransmission and combining of unsuccessfully received collided packets applying a truncated Hybrid Automatic Repeat reQuest (HARQ) scheme. For the first system, we propose to use channel realizations of collided packets as different signatures to separate them. Moreover, we propose a solution for the problem when the received powers are comparable. For this system, we note that the orthogonality of the STBC matrix allows the use of a simple linear processing step for the initialization of SSIC. For the SM multi-user system, the separation of collided packets is based on V-BLAST processing and SSIC. We also propose how to combine retransmitted packets. For both systems, we evaluate the block error rate, the throughput, and the delay. A comparison is done with the single-user case and with other receivers proposed in the literature.     

Stability and delay of finite-user slotted ALOHA with multipacket reception

The effect of multipacket reception (MPR) on stability and delay of slotted ALOHA based random-access systems is considered. A general asymmetric MPR model is introduced and the medium-access control (MAC) capacity region is specified. An explicit characterization of the ALOHA stability region for the two-user system is given. It is shown that the stability region undergoes a phase transition from a concave region to a convex polyhedral region as the MPR capability improves. It is also shown that after this phase transition, slotted ALOHA is optimal i.e., the ALOHA stability region coincides with the MAC capacity region. Further, it is observed that there is no need for transmission control when ALOHA is optimal i.e., ALOHA with transmission probability one is optimal. Next, these results are extended to a symmetric N>2 user ALOHA system. Finally, a complete characterization of average delay in capture channels for the two-user system is given. It is shown that in certain capture scenarios, ALOHA with transmission probability one is delay optimal for all stable arrival rates. Further, it is also shown that ALOHA with transmission probability one is optimal for stability and delay simultaneously in the two-user capture channel.     

Spread slotted ALOHA techniques for mobile and personal satellitecommunication systems

The objective is to develop a general theoretical framework for a class of spread slotted ALOHA (SSA) systems. The contributions include: modeling of a generalized spread slotted ALOHA (SSA) system; derivation of computationally efficient closed form expressions for the SSA system throughput and delay taking into account receiver complexity; and presentation of numerical results to validate the derivation as well as to substantiate the superior performance of the proposed scheme. The results demonstrate that SSA schemes offer significant improvements in terms of throughput, delay, and network stability against excessive loading at very acceptable levels of receiver implementation complexities. Also, SSA is found to be highly robust to errors in the time of arrivals and eliminates the need for a guard time     

Relation between transmission and throughput of slotted ALOHA localpacket radio networks

A new method for the exact calculation of the throughput of a centralized slotted ALOHA packet radio network over slow Rayleigh-fading channels is presented and the results are compared with the computer simulations. Also, upper and lower bounds on the performance are provided. The effects of capture on the throughput of the system are related to the modulation and coding technique, signal to noise ratio of the received signal, general terminal distribution in the area, and the length of the transmitted packets. The binary phase shift keying (BPSK), coherent and noncoherent binary frequency shift keying (FSK) modulations and BCH coding are considered for the exact calculations. The results of the analysis show that the maximum average throughput of the slotted Aloha packet radio network is around 60% rather than 36% predicted from the simplified analysis. In contrast with some previous reports, it is shown that the throughput of the system is not affected significantly by the use of coding or the change of packet lengths     

Capacity allocation for integrated voice/data transmission at apacket switched TOM

The integrated transmission of voice and data at a time-division multiplexer (TDM) is discussed and analyzed. The system operates in a frame format and the channel capacity is governed by the frame size. The allocation of channel capacity for the transmission of voice and data is performed by a controller. Digital speech interpolation (DSI) and embedded coding techniques are used to enhance the transmission efficiency and to facilitate the implementation of multiplexing. Using a dynamic programming approach, a capacity allocation policy which jointly optimizes the voice/data performance is introduced. Numerical results indicate that the aggregate throughput of the system can be improved with a slight degradation in voice quality     

Stabilised optimal operation for controlled slotted ALOHA

Criteria for choosing control parameters that stabilise an ALOHA system in the heavy traffic region are obtained by analysing the drift of the real and the estimated numbers of users. The control parameters ensure maximum channel utilisation and that the system operates at its optimum operating point     

Performance comparison of a slotted ALOHA DS/SSMA network and amultichannel narrow-band slotted ALOHA network

Throughput, delay, and stability for two slotted ALOHA packet radio systems are compared. One system is a slotted direct-sequence spread-spectrum multiple-access (DS/SSMA) network where each user employs a newly chosen random signature sequence for each bit in a transmitted packet. The other system is a multiple-channel slotted narrow-band ALOHA network where each packet is transmitted over a randomly selected channel. Accurate packet success probabilities for the code-division multiple-access (CDMA) system are computed using an improved Gaussian approximation technique which accounts for bit-to-bit error dependencies. Average throughput and delay results are obtained for the multiple-channel slotted ALOHA system and CDMA systems with block error correction. The first exit time (FET) is computed for both systems and used as a measure of the network stability. The CDMA system is shown to have better performance than the multiple-channel ALOHA system in all three areas     

Simple input control procedure for slotted ALOHA

A simple input control procedure using channel feedback information is presented. The steady state performance characteristics of slotted ALOHA with input control are evaluated. In particular, it is shown that the slotted ALOHA with input control has a unique stable steady state with high throughput.<>     

Framed slotted ALOHA with grouping tactic and binary selection for anti-collision in RFID systems

9%-16.3% compared to other ALOHA-based tag anti-collision algorithms when the number of tags is 1 000.     

Delay distributions of slotted ALOHA and CSMA

We derive the closed-form delay distributions of slotted ALOHA and nonpersistent carrier sense multiple access (CSMA) protocols under steady state. Three retransmission policies are analyzed. We find that under a binary exponential backoff retransmission policy, finite average delay and finite delay variance can be guaranteed for G<2S and G<4S/3, respectively, where G is the channel traffic and S is the channel throughput. As an example, in slotted ALOHA, S<(ln2)/2 and S<3(ln4-ln3)/4 are the operating ranges for finite first and second delay moments. In addition, the blocking probability and delay performance as a function of r/sub max/ (maximum number of retransmissions allowed) is also derived.     

Stabilization of slotted ALOHA spread-spectrum communicationnetworks

A method is presented for stabilizing slotted ALOHA frequency-hop communication networks by controlling code rate. In particular, the stabilization of a fully connected network in which a finite number of transmitter-receiver pairs exchange packets of information encoded by Reed-Solomon codes is considered. A principle of flow balance to stability analysis is adopted, and it is shown that network stability can be ensured by controlling code rate. The requirement on code rate for ensuring network stability is examined. In addition, the mean delay and the mean channel throughput of the network are discussed     

Delay versus throughput comparisons for stabilized slotted ALOHA

Methods of stabilizing the slotted ALOHA channel are simulated to compare delay versus throughput performance. It is shown that the best performance is provided by methods that use deferred first transmission and estimate the number of blocked terminals. Three such methods, previously thought to be independent, are shown to be the same scheme with different control parameters. It is shown that these three methods do not differ in delay vs. throughput performance at the 95% confidence level. The optimal parameters to provide the smallest delay at a given throughput are explored, and it is shown that near-optimal parameters provide a smaller delay than that obtained using previously published schemes     

Analysis of an integrated voice and data transmission system usingpacket reservation multiple access

Packet reservation multiple access (PRMA) is a channel access protocol proposed for the third generation wireless information networks which have attracted considerable attentions recently. By using the equilibrium point analysis (EPA), a PRMA integrated voice and data system has been studied in previous research. However, the error between numerical results of the analysis and those of simulation is relatively large. In this paper, we also study an integrated voice and data system with PRMA. The system performance is evaluated by using a Markov analysis method. First, some analytic models are constructed such that the system transition can be described by a Markov chain. Then, we calculate the entries of the one step state transition matrix using an iterative procedure. Finally, system performance measures, such as throughput and delay, are evaluated. Little error between numerical results of analysis and those of simulation indicates that the method is appropriate to analyze PRMA systems,     

Integrated voice/data multiplexers with slotted and nongated packetservices

Integrated voice/data multiplexers that provide packet services for both voice and data traffic are discussed. A slotted service is assumed, so that packet transmissions are synchronized to slot boundaries. Nongated service, in which packets are transmitted as soon as the transmission capacity becomes available, is also assumed. The performance of nongated and slotted multiplexers is obtained by analytic and simulation approaches. In particular, a PRIO (head-of-the-line priority to voice packets) and a BVFD (busy-voice, fixed-data) multiplexer are shown to be suitable for such a nongated environment     

Capacity, throughput, and delay of slotted ALOHA DS-CDMA links with adaptive space-time auxiliary-vector receivers

We investigate the user capacity, throughput, and delay characteristics of a mobile slotted ALOHA direct-sequence code-division-multiple-access (DS-CDMA) link with dedicated signatures under multipath fading and packet-rate adaptive antenna array signal reception. For a given system transmission bit rate, the packet size is designed to be sufficiently small to conform with the coherence time of the channel. Then, on an individual packet-by-packet basis, a phase-ambiguous spatial-temporal channel estimate is produced by a blind (unsupervised) eigensubspace procedure. The space-time channel estimate is phase corrected via a few pilot packet mid-amble bits and used for joint spatial-temporal multiple-access-interference suppression according to the principles of auxiliary-vector filtering. Subsequently, packet success probabilities are derived in the presence or absence of forward error correction and are used to evaluate the throughput and delay characteristics of the link.     

Analysis of mobile radio slotted ALOHA networks

Given a mobile terminal transmitting a message to some receiver, the level at the receiver will be affected by path loss and by fading phenomena. Transmissions from different terminals will suffer different attenuations on their respective ways to the receiver and will therefore yield different levels at the receiver. Thanks to the capture effect, the receiver will now be able to read the message with the strongest signal, provided that it is sufficiently stronger than its contenders. In a mobile radio ALOHA network this means that a packet collision need not necessarily destroy all packets involved. A Markov model is developed for slotted ALOHA networks with capture and it is shown that the throughput in such a network can be markedly greater than the famous 1/e. Perhaps even more important is the result that such networks are very stable under overload.     

CLSP with channel clearance for spread slotted ALOHA network

A new CLSP with channel clearance (CLSP/CC) is proposed for obtaining better network performances in spread slotted ALOHA networks. This protocol can decrease wasteful channel usage by prohibiting continuous transmissions of packets already destroyed in previous slot, with little added network complexities. To validate the performance improvements of our protocol, both simulation and analysis are considered. As a result. The network using the proposed CLSP/CC is superior to that with CLSP, and also to the conventional one, especially when the system capacity is half of the offered load, and improves as the threshold for CLSP increases to network capacity     

Access control of data in integrated voice/data CDMA systems:benefits and tradeoffs

In previous work, access control for data has been proposed as a method to ensure adequate quality of service (QoS) in an integrated voice/data CDMA system. The motivation behind access control is to schedule data packet transmissions in slots when voice activity is low and to curtail data transmissions when the voice load is heavy. In this work, the class of probabilistic access control schemes, wherein data transmissions are controlled by dynamically changing the permission probability, are considered. The trigger for changing the permission probability is a measure of the current uplink load. Perfect power control is assumed first, and the trigger for access control is the power control feasibility condition, Schemes based on prediction are analyzed. While prediction schemes are complex to implement, they do provide an upper bound for performance of access control schemes. A simple and practical access control scheme, proposed earlier in the literature, is then extended. It controls the permission probability for data based on uplink load and a 1-bit broadcast feedback to all of the mobiles. The performance of this scheme depends on the choice of three parameters. It is demonstrated that, through a combined choice of these parameters, access control can be tuned to perform as desired and to yield significant capacity gains over not using access control. Results are then extended to the case of imperfect power control, where the outage criterion is based on limiting the total received power at the base station. In this case, too, the simple control scheme is shown to work well     

A cooperative Bayesian and lower bound estimation in dynamic framed slotted ALOHA algorithm for RFID systems

A novel estimation scheme that combines Bayesian and lower bound estimating radio frequency identification tag population size is proposed. The developed methodology is based on the fusion between the Bayesian and lower bound estimating techniques. It turns out that the fusion rule is built up thanks to an existing linear relationship between the cited techniques. Simulation results show that the developed technique significantly improves the accuracy of the estimating tag quantity and presents less estimation error. Also, the resulting advanced dynamic framed slotted ALOHA protocol considerably improves the performance and efficiency of the radio frequency identification anti‐collision compared with the most recent protocols using others estimating methods.