24 research outputs found
Soft Handoff and Uplink Capacity in a Two-Tier CDMA System
This paper examines the effect of soft handoff on the uplink user capacity of
a CDMA system consisting of a single macrocell in which a single hotspot
microcell is embedded. The users of these two base stations operate over the
same frequency band. In the soft handoff scenario studied here, both macrocell
and microcell base stations serve each system user and the two received copies
of a desired user's signal are summed using maximal ratio combining. Exact and
approximate analytical methods are developed to compute uplink user capacity.
Simulation results demonstrate a 20% increase in user capacity compared to hard
handoff. In addition, simple, approximate methods are presented for estimating
soft handoff capacity and are shown to be quite accurate.Comment: To appear in IEEE Transactions on Wireless Communication
Network congestion management using Call Admission Control
Abstract: Call Admission Control schemes have been used extensively in improving mobile network quality. Signal quality degradation, interference and network congestion has been a real issue for Global System for Mobile Communication (GSM) as the number of mobile users increased rapidly. It has been an issue in providing a decent Quality of Service (QoS) to the network users especially during the period of high network traffic. It is essential to maintain a certain level of quality in handling mobile network congestion. Fortunately, Call Admission Control is a strategy that can provide credible QoS by limiting the number of connections into the cellular network thereby reducing network congestions, dropping of calls, interference and other QoS problems. In this paper, we discuss issues around mobile network congestion, overview of congestion management schemes, attributes and benefits of Call Admission Control (CAC). We also highlight different handoff schemes. We simulated a typical CAC scheme comparing the new call blocking probability and handoff call probability
WCDMA downlink capacity of cigar-shaped microcells using soft hand-over with SIR-based power control for over-ground train service
In this paper, the downlink sector capacity of a cigar-shaped microcells using wideband code-division multiple-access (WCDMA) with soft hand-over (SHO) mode is analyzed. The two-slope propagation loss with log-normal shadowing is used in the analysis where a model of eight cigar-shaped microcells is utilized to calculate the downlink sector capacity. The performance of the downlink is studied for different sector radii, standard deviations of the shadowing and propagation exponents. It is found that, for a sector range higher than 940 m, increasing the sector range will reduce the downlink sector capacity. Also it is found that increasing the value of the propagation parameters will reduce the downlink sector capacity. In many cases, the downlink sector capacity will be code limited since the theoretical downlink sector capacity is higher than the number of codes assigned to each sector. The high theoretical downlink sector capacity is due to the low value (0.06–0.1) of the WCDMA orthogonality factor of rural zone microcells
WCDMA multiclass downlink capacity and interference statistics of cigar-shaped microcells in highways
The final publication is available at Springer via http://dx.doi.org/10.1007/s11277-013-1048-5In this paper, the multiclass downlink capacity and the interference statistics
of the sectors of a cigar-shaped microcells using wideband code-division multiple-access
with soft handover mode are analyzed. The two-slope propagation model with log-normal
shadowing is used in the analysis where a model of 8 cigar-shaped microcells is utilized. The
performance of the downlink is studied for different [sector range R, standard deviation of
the shadowing (σ1 and σ2) and propagation exponents (s1 and s2)]. It is found that increasing
the sector range from 500 to 1,000 m will increase the sector downlink capacity. Also, it is
found that increasing the value of the propagation parameters (σ1 and σ2) will reduce the
downlink sector capacity. It is noticed that, the effect of changing the propagation exponent
s1 is null while increasing the propagation exponent s2 will increase the downlink capacit
Capacity Analysis in Downlink WCDMA Systems Using Soft Handover Techniques With SIR-Based Power Control and Site Selection Diversity Transmission
This work analyzes the downlink performance of a WCDMA system with
site selection diversity transmission power control (SSDT) during soft handover mode. Signal to
interference ratio (SIR) power control techniques are modeled and used in the simulations of this
analysis. The study is focused on finding the optimum soft handover margin in terms of
maximum system capacity under energy-per-bit to noise spectral density ratio (Eb/N0) quality
requirements. The results of this analysis show an increase in user capacity of about 15 -20 % for
optimum soft handover margins of 5 – 5.5 dB. Nevertheless, the resources required (number of
scrambling codes) by base station increase faster than the number of active users in terms of soft
handover margin up to soft handover margin values of approximately 9.5 dB.Reig, J. (2006). Capacity Analysis in Downlink WCDMA Systems Using Soft Handover Techniques With SIR-Based Power Control and Site Selection Diversity Transmission. IEEE Transactions on Vehicular Technology. 55(4):1362-1372. doi:10.1109/TVT.2006.877705S1362137255
Competition of Wireless Providers for Atomic Users: Equilibrium and Social Optimality
We study a problem where wireless service providers compete for heterogenous and atomic (non-infinitesimal) wireless users. The users differ in their utility functions as well as in the perceived quality of service of individual providers. We model the interaction of an arbitrary number of providers and users as a two-stage multi-leader-follower game, and prove existence and uniqueness of the subgame perfect Nash equilibrium for a generic channel model and a wide class of users' utility functions. We show that, interestingly, the competition of resource providers leads to a globally optimal outcome under fairly general technical conditions. Our results show that some users need to purchase their resource from several providers at the equilibrium. While the number of such users is typically small (smaller than the number of providers), our simulations indicate that the percentage of cases where at least one undecided user exists can be significant
Supporting vehicular mobility in urban multi-hop wireless networks
Deployments of city-wide multi-hop 802.11 networks introduce challenges for maintaining client performance at vehicular speeds. In this thesis, we experimentally demonstrate that current network interfaces employ policies that result in long outage durations, even when clients are always in range of at least one access point. Consequently, we design and evaluate a family of client-driven handoff techniques that target vehicular mobility in multi-tier multi-hop wireless mesh networks. Our key technique is for clients to invoke an association change based on (i) joint use of channel quality measurements and AP quality scores that reflect long-term differences in AP performance and (ii) controlled measurement and hand-off time scales to balance the need for the instantaneously best association against performance penalties incurred from spurious handoffs due to channel fluctuations and marginally improved i associations. We utilize a 4,000 user urban deployment to evaluate the performance of a broad class of hand-off policies