Estimating path loss for a transmitter-receiver location is key to many use-cases including network planning and handover. Machine learning has become a popular tool to predict wireless channel properties based on map data. In this work, we present a transformer-based neural network architecture that enables predicting link-level properties from maps of various dimensions and from sparse measurements. The map contains information about buildings and foliage. The transformer model attends to the regions that are relevant for path loss prediction and, therefore, scales efficiently to maps of different size. Further, our approach works with continuous transmitter and receiver coordinates without relying on discretization. In experiments, we show that the proposed model is able to efficiently learn dominant path losses from sparse training data and generalizes well when tested on novel maps.

Directional beamforming with large antenna arrays is key to mitigating the substantial signal loss experienced at the millimeter wave frequency band, important to fifth generation (5G) cellular systems and next generation wireless local area networks, where it entails a significant increase in the number of beams. This paper is motivated by the realization that the underlying problem of finding the optimal set of beam steering directions will benefit from fundamental signal processing methodologies, and specifically from basic principles and algorithms for cluster analysis. Earlier work by authors established the equivalence between the problem of optimizing a set of beam steering directions and the classical problems of clustering and quantizer design, albeit with an unusual distortion measure. Subsequently in [1], a k-means-like approach was derived to optimize beam steering directions and guarantee convergence to at least locally optimal solution. The main contribution of this work is the derivation of a global optimization approach within the deterministic annealing framework, to circumvent poor local optima that riddle the cost surface. Simulation results show that the approach delivers considerable gains over the baseline uniform beam steering technique, specifically, up to 6 dB and 13 dB gains, in terms of average and 10th percentile of the power array factor, respectively, as well as up to 6.5 dB gain in the average Signal-to-Noise Ratio (SNR).

In order to increase system capacity and transmission rates, fifth-generation (5G) cellular and 802.11ad/ay wireless systems will use millimeter wave frequencies (24GHz-70GHz), which require large antenna arrays and narrow beamforming to mitigate the impact of substantial path-loss. While narrow beamforming maximizes array gain it also entails a significant increase in the number of beams needed to maintain the desired cell coverage. Consequently, there is a considerable increase in the complexity of beam management for initial user access and then tracking. This paper proposes a novel beam steering algorithm to maximize coverage given a prescribed size for the codebook of beam directions. The proposed approach leverages the observation that the problem of finding the optimal set of beam pointing angles can be mapped to the classical quantizer design problem in source coding, albeit with a somewhat unusual distortion measure. A variant of the Generalized Lloyd Algorithm is derived and employed to find the optimal codebook of beam placement angular directions. Numerical results show up to 2 dB gains in average power array factor, in comparison with the conventional uniformly spaced beam steering approach. These performance gains can be traded for codebook size reduction and a corresponding reduction in beam management complexity.

Fifth generation (5G) wireless systems will use higher frequency bands (24GHz-70GHz), the so-called millimeter wave frequencies in order to achieve higher capacity. These systems rely on using large antenna arrays and narrow beamforming to counter the large path-loss experienced. Narrow beamforming maximizes array gain but results in a significant increase in beam management complexity, and is sensitive to channel dynamics as well. This, in-turn attracted attention towards beam-broadening algorithms, where a trade-off between high transmission quality and robustness can be achieved. In this paper, a novel beam-broadening algorithm based on Sequential Quadratic Programming (SQP) is proposed. Numerical results show up to 3 dB performance gain in comparison to competing beam broadening algorithms. It is worth noting that the performance gain is achieved at no additional cost.

In order to achieve higher transmission rates and system capacity, fifth-generation cellular (SG) and 802.11ad/ay wireless systems will use higher frequency bands (24GHz-70GHz), the so-called millimeter wave frequencies. These systems rely on using large antenna arrays and narrow beamforming to counter the large path-loss experienced. Narrow beamforming maximizes array gain but results in a significant increase in beam management complexity, and the number of beams which are required to maintain the desired cell coverage as well. Hence, beam-broadening algorithms are suggested as a countermeasure, where a trade-off between high transmission quality and robustness to dynamics could be achieved. In this paper, a novel beam-steering algorithm is proposed to achieve improved coverage for a defined codebook size. Additionally, indoor office system performance is evaluated for different beamforming techniques. Numerical results show up to 1.5 dB improvement in system Signal-to-Interference-plus-Noise Ratio (SINR) via the proposed beam-steering approach when compared to conventional methods. The SINR gains could be converted to a 35% reduction in codebook size. These improvements are attained at zero additional cost.

High spatial reuse through densification of wireless networks and higher amount of bandwidth are necessary to meet the increase of wireless demand in the next decade. Small cells that operate at millimeter wave (MMW) band can fulfill these two criteria. Deploying fiber to many small cell MMW base stations can be expensive and wireless backhaul can reduce this cost. A fixed access backhaul network - where the available resource is fixed separately for access and backhaul links - cannot meet the dynamic traffic demand of the network. An integrated access backaul (IAB) network - where the summation of available resource is fixed for access and backhaul links - can dynamically change the partition between access and backhaul links and meet instantaneous demand of UEs acrosss the network. This work focuses on joint cost optimal fiber drop deployment, resource allocation and routing in an IAB network. Simulation results show that IAB can significantly reduce the fiber drop deployment cost of the network compared to fixed access backhaul network.

Given the cost and complexity associated with the deployment of a large number of radio frequency (RF) chains in millimeter wave (mmW) multi-input multi-output (MIMO) systems, this paper addresses the question of network efficiency considerations for hybrid precoding. We first establish the relevance of directional precoding structures as a low-complexity and robust solution to meet the data rate demands of single-user MIMO systems relative to the more complex and less robust eigen-mode-based precoding structures. Key to the relevance of the directional precoding structures is the sparsity of the mmW channel coupled with higher antenna dimensionality affordable due to smaller wavelengths. We then leverage the directional structure of the channel to propose a simple class of directional schedulers that offers a low-complexity and yet approximately fair separation plane in the user space. We then compare the performance of single-user precoding schemes with multi-user precoding schemes and show that from network efficiency considerations, it would be more worthwhile to expend the RF chain resource on multi-user transmissions.

The focus of this work is on cost and complexity- induced rank-constrained precoding for millimeter- wave (mmW) multi-input multi-output (MIMO) systems. The higher antenna dimensionality and sparse channel structure of mmW systems motivate directional precoding schemes over more complex and less robust eigen-mode-based precoding schemes. Building on a prior work that illustrated the superiority in design, robustness and performance of a directional rank-1 beamformer, this work considers higher-rank directional precoding structures for mmW systems. It is shown that directional precoders continue to enjoy similar properties in single-user MIMO (SU-MIMO) systems. But from a network efficiency consideration, it would be more worthwhile to expend the radio frequency (RF) chain resource on multi-user transmissions. Towards this goal, a directional scheduler and different directional beamforming structures are proposed here. These structures are shown to result in significant performance improvement over higher-rank SU-MIMO schemes.

High user density in stadiums and auditoriums is a challenging scenario for deploying future generation wireless networks. Due to the almost line-of-sight propagation model, the LTE base stations and WiFi access points would interfere with each other and result in reduced throughput in this scenario. Millimeter and microwave bands can play an important role in this regard due to their spatial reuse capability. This paper focuses on the coverage and capacity of the 28 GHz band in indoor stadiums and auditoriums. We model an indoor basketball stadium and human blockage loss. We consider two different types of human blockage models: (i) knife edge diffraction model and (ii) experimental blockage model. We develop the experimental blockage model while making measurements in a small-scale stadium-like seating area. Our experiments suggest that the boresight direction is irrelevant in the presence of multiple surrounding scattering objects. Scattering and reflections of signals from neighboring human bodies can provide strong signal paths at the millimeter wave band in indoor stadiums. Based on this model, we simulate the connectivity of the 28 GHz band with different sitting and standing patterns among audience. Simulation results suggest that ten base stations can sustain a sum rate of 76 Gbps and 227 Gbps with one and four RF chains respectively in 50 percentile case. We also show that the 28 GHz's sustainable data rate can be 11 and 33 times higher than the 5 GHz's sustainable data rate with one and four RF chains respectively.

The focus of this paper is on beamforming in a millimeter-wave (mmW) multi-input multi-output (MIMO) set-up that has gained increasing traction in meeting the high data-rate requirements of next- generation wireless systems. For a given MIMO channel matrix, the optimality of beamforming with the dominant right-singular vector (RSV) at the transmit end and with the matched filter to the RSV at the receive end has been well-understood. When the channel matrix can be accurately captured by a physical (geometric) scattering model across multiple clusters/paths as is the case in mmW MIMO systems, we provide a physical interpretation for this optimal structure: beam steering across the different paths with appropriate power allocation and phase compensation. While such an explicit physical interpretation has not been provided hitherto, practical implementation of such a structure in a mmW system is fraught with considerable difficulties (complexity as well as cost) as it requires the use of per-antenna gain and phase control. This paper characterizes the loss in received SNR with an alternate low-complexity beamforming solution that needs only per-antenna phase control and corresponds to steering the beam to the dominant path at the transmit and receive ends. While the loss in received SNR can be arbitrarily large (theoretically), this loss is minimal in a large fraction of the channel realizations reinforcing the utility of directional beamforming as a good candidate solution for mmW MIMO systems.

In this paper, we conduct ray-tracing simulation studies using WinProp tool to understand the path loss, coverage area, diversity and delay spread of the 29GHz band in the indoor propagation environment, and compare the 29GHz indoor channel to the 2.9GHz indoor channel. In addition, we compare our simulation results with the measurement data from [4]. Based on our simulation results, we conclude that the 29GHz band has similar indoor channel characteristics as 2.9GHz and that any inherent impairment of the mmWave due to higher carrier frequency can easily compensated with beam forming techniques and other advanced algorithms. Specifically, our results show that the path loss exponents and the RMS delay spread values are similar at 29GHz and at 2.9GHz. In addition, our simulation results show that by having multiple access points on an office floor, we can significantly improve important diversity metrics such as the number of detectable beams and the angular separation of those beams, so as to make 29GHz system using beam forming technique more robust against beam blockage.

Utilization of millimeter wave (MMW) bands for supporting very high data rate cellular access has received much attention in recent times. The behavior of the wireless channel in these bands differ significantly from the sub-6 GHz counterparts. Ray tracing is a complementary effort to detailed measurements in providing quick insight into the coarse channel characteristics. In this paper, we model the 28 GHz outdoor channel through ray tracing using the WinProp tool. We simulate the single base station and multi base station scenarios in the downtown Manhattan area and study channel properties such as coverage and path loss, path diversity and delay spreads. We observe that a typical MMW base station provides coverage to a significant fraction of a 100m cell radius with path diversity, i.e. there exist secondary paths that may sustain the link on the failure of the first path. The improvements to coverage and path diversity with multiple base stations are also characterized. The above channel properties are compared with NYU's [4] results from the same region. We observe a reasonable match for many of the above parameters. The delay spreads with omni and beamformed antennas are also compared. The typical RMS delay spread in a beamformed scenario is seen to be in the order of 20-30 ns which is significantly smaller than the measured values of 100ns or more. This phenomenon is likely due to detailed clutter in the environment not being modeled.

The distributed coordination function (DCF) for 802.11 medium access control (MAC) leads to poor spatial spectral reuse and results in low user throughput in dense user settings. In this paper, we consider simple modifications to the carrier sense mechanism that substantially improve the bits/sec/Hz/area, without increasing transceiver complexity. For 802.11g and 802.11ac, we augment the CTS with channel gain information and modify the virtual and physical carrier sense for the duration of NAV in the CTS. In addition, we consider a roughly synchronized network with alternate control and data transmission phases. During the control phase, a carrier sense multiple access with collision avoidance (CSMA-CA) MAC is used to exchange a few RTS-CTS messages in a local network neighborhood to determine the transmission scheme in the ensuing data phase. Our methods enable the application of signal to interference and noise (SINR) based scheduling algorithms to WiFi networks resulting in tremendous increase in throughput and QoS/fairness.

We consider wireless femtocell networks where scheduling of transmissions is coordinated across multiple cells to mitigate interference and deliver fairness and quality of service (QoS). Coordination across multiple cells entails (i) exchange of (serving and interfering) channel information and traffic priority (which is a function of packet delays, average rate, queue length), and (ii) signalling of transmission powers over pilots so that neighboring cells can determine the expected SINR to pick the right modulation and coding scheme. Such an exchange entails delay in coordination, resulting in scheduling decisions being made on the basis of stale information received from other cells. In this paper, we study aspects of practical signalling and algorithm design to account for such coordination delay and study its impact. When the coordination across cells is done over a high latency backhaul, we design a hybrid signalling mechanism where minimal amount of additional over-the-air (OTA) signalling enhancement can lead to tremendous performance improvement. We numerically demonstrate the benefits of our approach via comparison to a centralized scheduler and reuse one scheme using system simulations based on 3GPP evaluation methodology.

We design novel mechanisms and algorithms for fast, simple, and distributed interference management and scheduling in wireless femto networks via exchange of information over-the-air (OTA). We focus on Long Term Evolution (LTE) of the 3GPP standard and on the downlink; we leverage the existing signalling in LTE and delineate additional signals that are needed. Key aspects of our work include: (1) the design is based on only one round of exchange of very few bits of information in each subframe (of 1 ms), (2) the algorithm is a heuristic derived from the maximum weight scheduling algorithm for a realistic interference model, and (3) the framework allows for easy control of fairness for best effort flows, control of delay tails for delay sensitive QoS flows, and relative prioritization between best effort and QoS flows. The performance of the mechanisms and algorithms is validated using system simulations based on 3GPP evaluation methodology.

Embedding pico/femto base-stations and relay nodes in a macro-cellular network is a promising method for achieving substantial gains in coverage and capacity compared to macro-only networks. These new types of base-stations can operate on the same wireless channel as the macro-cellular network, providing higher spatial reuse via cell splitting. However, these base-stations are deployed in an unplanned manner, can have very different transmit powers, and may not have traffic aggregation among many users. This could potentially result in much higher interference magnitude and variability. Hence, such deployments require the use of innovative cell association and inter-cell interference coordination techniques in order to realize the promised capacity and coverage gains. In this paper, we describe new paradigms for design and operation of such heterogeneous cellular networks. Specifically, we focus on cell splitting, range expansion, semi-static resource negotiation on third-party backhaul connections, and fast dynamic interference management for QoS via over-the-air signaling. Notably, our methodologies and algorithms are simple, lightweight, and incur extremely low overhead. Numerical studies show that they provide large gains over currently used methods for cellular networks.

To improve spectrum efficiency, future wireless devices will use cognitive radios to dynamically access spectrum. While offering great flexibility and software-reconfigurability, unsecured cognitive radios can be easily manipulated to attack legacy and future wireless networks. In this paper, we explore the feasibility and impact of cognitive radio based jamming attacks on 802.11 networks. We show that attackers can utilize cognitive radios' fast channel switching capability to amplify their jamming impact across multiple channels using a single radio. We also examine the impact of hardware channel switching delays and jamming duration on the impact of jamming.

Availability is an important attribute of optical transport networks, and is enabled through many alternative restoration schemes. Different restoration schemes tradeoff network cost, as measured by provisioned capacity, and network reliability to match diverse application needs. We provide a systematic quantification of these tradeoffs for commonly employed restoration schemes and illustrate them for several networks. In this paper, we analyze a dedicated capacity 1+1 protection scheme and two commonly employed shared capacity mesh restoration schemes: path and link based restoration

Wireless systems, such as UMTS, use a paging indication channel (PICH) to signal whether a mobile is being paged. The threshold for PICH detection must he set to balance the tradeoff between missed calls (due to missed page) and lowered battery life (due to false alarms). Threshold selection is one of many factors that affect those metrics and, often, the sensitivity of those metrics to the PICH detection performance is highly dependent on the operating SNR. The paper provides a methodology for automatically setting the PICH detection threshold by taking such an SNR dependent sensitivity of the performance metrics into account in order to achieve the right tradeoff across all SNRs. Furthermore, we correctly account for imperfect channel estimation in the threshold setting. For each SNR value, we determine which metric (the metrics are false alarm probability and missed PICH probability) is the binding constraint and determine what its value should be. Using an analytic approach that correctly accounts for channel estimation error, we then determine the appropriate threshold to use at that SNR. Simulation results are presented for a UMTS system and show that substantial improvements in battery life can be obtained while also improving missed call rate compared to maximum likelihood (ML) detection. Significant gains over a Neyman-Pearson (NP) based approach are also obtained.

An expanded effort is underway to support the evolution of the UMTS standard to meet the rapidly developing needs associated with wireless Internet applications. The support of high speed downlink packet access (HSDPA) is provided by means of a new, shared channel called high speed downlink shared channel (HS-DSCH) which is enabled by a number of performance enhancing technologies such as adaptive modulation and coding (AMC), hybrid ARQ (HARQ), fat-pipe scheduling, fast cell selection (FCS) and multiple input multiple output (MIMO) antenna techniques. In this paper, the advantage of FCS is investigated. To avoid the difficulty in HARQ transmission-state synchronization, FCS is allowed only among the cells (sectors) belonging to the same base station. Two FCS approaches are compared in this paper. The user controlled cell selection (UCCS) selects the serving cell based only on the channel quality seen by the user. While a new-network controlled cell selection (NCCS) approach jointly considers channel quality and network loading. It is shown that FCS significantly improves the HSDPA performance at low mobility. Among the FCS schemes, NCCS is superior to UCCS when the load among the cells in the active set is unbalanced.

A link error prediction (LEP) methodology allows the abstraction of link performance into system level studies, so that system performance may be characterized efficiently. The quasi-static method (QSM) method (http://www.3gpp2.org) (R. Ratasuk et al., 2002) which assumes perfect channel quality estimates for demodulation, has been widely used for downlink system performance evaluation. However, unlike in the downlink, the per-user uplink pilot, which is power-controlled, is much weaker, so that channel estimation errors, and its effect on link performance (especially at high data rates), is considerably higher. In this paper we propose a simple and efficient LEP method, which we call the equivalent SNR method (ESM), for analytically capturing the effect of channel estimation errors on link performance. ESM is shown to he extremely accurate over a wide range of pilot SNRs. We note that ESM was adopted for LEP for cdma2000 (EVDV) and UMTS system simulations.

An expanded effort is underway to support the evolution of the UMTS and cdma2000-1x standards to meet the rapidly developing needs associated with wireless Internet applications. A number of performance enhancing technologies are proposed to ensure high peak and average packet data rates while supporting circuit-switched voice and packet data on the same spectrum. These techniques include adaptive modulation and coding (AMC), hybrid ARQ (H-ARQ) and fat-pipe scheduling. In order to enable these techniques downlink channel quality feedback (CQF) through explicit uplink signaling is necessary. Frequent CQF results in good estimates of downlink channel quality at the base station, which, in turn, improves downlink system performance. However, this comes at the expense of larger uplink signaling overhead, thereby impacting the overall uplink capacity. Infrequent CQF, on the other hand, reduces this signaling overhead in the uplink at the expense of larger errors in the channel quality estimates available at the base station, thereby leading to system performance degradation. In this paper, we present a variable rate CQF scheme that significantly reduces uplink signaling overhead without affecting downlink system performance. In addition to simulation results demonstrating the performance of the proposed scheme, we also compare the reduction in uplink signaling overhead of the said scheme with other known methods.

Universal Mobile Telecommunications System (UMTS) networks are capable of serving packet-switched data applications at bit rates as high as 384 kbps. This paper studies the capacity and utilization of the downlink of the Iub interface, which lies between the radio network controller (RNC) and the base station (NodeB) in the UMTS network. The 3GPP standards define a Node B "receive window" within which a frame should arrive for it to be processed and transmitted to the UE in time. If the frame arrives too late, it will be discarded. Such frame discard event results in some loss in voice/data quality. Via simulations, we evaluate the link capacity for web-browsing traffic at 64 kbps, 128 kbps and 384 kbps, with a frame discard probability target of 0.5%. Our results indicate that the Iub link utilization is very poor due to the highly bursty nature of data traffic. In order to alleviate this problem, we introduce a rate control (RC) scheme where the peak user data rate is temporarily lowered during times of high congestion. This lowering of data rate is done through appropriate selection of the transport block size within the transport format set. As a result of such rate control, the capacity of the Iub link improves.

In anticipation of the high demand for wireless data services, several wireless standards are evolving to support packed data more efficiently. In UMTS, a new, shared channel called the high speed downlink shared channel (HS-DSCH) that multiplexes packet data users has been defined. Several performance-enhancing technologies are included in high speed downlink packet access (HSDPA): adaptive modulation and coding (AMC), hybrid ARQ (HARQ), scheduling etc. HARQ algorithm plays a critical role in HSDPA performance. HARQ techniques are classified in terms of the combining method (chase or incremental redundancy, IR), protocol timing (synchronous or asynchronous) and adaptivity (if modulation/code-rate can be changed for retransmission or not). In previous work (Das et al. 2001), an adaptive, asynchronous, incremental redundancy (A/sup 2/IR) scheme was proposed and shown to provide substantial gains over other HARQ options. In this paper, the design and performance aspects of A/sup 2/IR in the code domain (as against the time domain in Das et al.) are considered. Due to the higher bandwidth of the UMTS channels compared to cdma2000 or HDR, it is expected that code-division multiplexing (CDM) of users will be needed to "fill the data pipe" instead of pure time-division multiplexing. The paper also analyzes tradeoffs that are unique to implementing A/sup 2/IR with CDM. A/sup 2/IR with a fixed TTI is now part of UMTS Release 5.

An expanded effort is underway to support the evolution of the UMTS standard to meet the rapidly developing needs associated with wireless Internet applications. The support of high-speed downlink packet access (HSDPA) is provided by means of a new, shared channel called high speed downlink shared channel (HS-DSCH) which is enabled by a number of performance enhancing technologies such as adaptive modulation and coding (AMC), hybrid ARQ (HARQ), fat-pipe scheduling, fast cell site selection (FCSS) and multiple input multiple output (MIMO) antenna techniques. To fully benefit from these technologies, one must guarantee fast and reliable control message exchange between the base station and the user terminals. The downlink signaling is done through the use of shared control channels (SCCH) accompanied with each HS-DSCH. Since the SCCHs, HS-DSCH, and voice channels share the same resources (power, bandwidth), control signalling is often improved at the cost of system resources and capacity. In this paper, we evaluate the performance of the SCCH. The challenges and tradeoffs in the SCCH design will also be discussed.

The signal-to-interference ratio (SIR) is an important metric of communication link quality. For wireless data systems SIR estimates are used in several control actions and for optimal allocation of radio resources. This paper first develops SIR estimators based on pilot symbols and then extends the results to estimators based on data symbols. It is shown that long-term smoothing of the interference variance estimates improves the overall estimation accuracy. Since both pilot and data symbols are available, estimators that optimally combine estimates from both types of symbols are also considered. In all cases, approximate analytic results are provided and validated using simulations. The analytic expressions serve two purposes. Firstly, improved estimators based on bias correction become apparent from the expressions and secondly, optimal weights for combining pilot and data based estimators can be evaluated. Results show that modest to substantial improvement in estimation accuracy is possible through optimal combining.

An expanded effort is underway to support the evolution of the UMTS standard to meet the rapidly developing needs associated with wireless Internet applications. The support of packet-switched high-speed data users is provided by means of a new, shared channel called HS-DSCH (high speed downlink shared channel) that preferably serves one packet data user at a time in a time-multiplexed manner. A number of performance enhancing technologies are included in the high speed downlink packet access (HSDPA) proposal to ensure high peak and average packet data rates while supporting circuit switched voice and packet data on the same spectrum. These techniques include adaptive modulation and coding (AMC), hybrid ARQ (HARQ), fat-pipe scheduling, fast cell site selection (FCSS) and multiple input multiple output (MIMO) antenna techniques. In this paper, we provide the performance comparison of different HARQ schemes being considered for HSDPA.

In previous work, access control for data was proposed as a method to enhance capacity while ensuring adequate quality of service (QoS) in an integrated voice/data CDMA system. The motivation behind access control is to schedule data packet transmissions when voice activity is low and curtail data transmissions when the voice load is heavy. In this work, a simple and flexible real-time access control scheme proposed in previous work, is extended. The performance measures used are the probability of outage and delay for data. It is shown how the system can support more users with access control than without, for a given probability of outage. The penalty lies in introducing delay for the data users. Performance of the control schemes is analyzed for different parameters and tradeoffs involved in their choice are discussed. It is demonstrated that with appropriate choice of parameters, the proposed real-time control scheme approaches the performance of optimum prediction schemes, in terms of the tradeoff between capacity and delay.

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.

Future wireless systems will have to support multimedia services such as voice, data and fax. Issues in providing multimedia services on wireless include multiple access, bandwidth rationing and power control. We address the latter two issues. CDMA is assumed to be the access method. Different services have different quality (QoS) requirements, maximum power and/or minimum rate constraints. In order to achieve the required QoS they can alter their power and/or rate of transmission. Different rates are represented by varying the processing gain. Since users interfere with each other, achieving each user's QoS requirement is completely coupled with the powers. We formulate this as a constrained optimization problem. The objective functions used are minimum power and maximum rates. The former reduces interference seen by other cells due to the current cell, the latter attempts to achieve the best possible throughput for users in the current cell. We develop bounds on the total number of users of each class that can be supported simultaneously while maintaining adequate QoS and meeting resource constraints.