Mats Blomgren

Downtilted Base Station Antennas - A Simulation Model Proposal and Impact on HSPA and LTE Performance

This paper proposes a low-complexity model for vertical antenna radiation patterns, e.g. for inclusion in system- level simulations. They can be seen as extensions to the horizontal radiation pattern model used in 3GPP simulation scenarios. The model is verified against and compared to predicted and measured data from real networks. The impact on system-level performance is also investigated. It is seen that using the proposed model, simulated geometry distributions and soft handover statistics closely matching those of real networks may be achieved. The analysis also concludes that many real networks have better cell isolation than what is modeled by the 3GPP antenna model. As a consequence, the horizontal radiation pattern model significantly under-estimates the system level performance in such networks. Furthermore, the proposed model is used to assess the LTE and HSPA system-level performance for realistic scenarios.

Stability of rate and power control algorithms in wireless cellular networks

In radio resource management for cellular networks a trade-off has to be made between the congestion level, related to cell coverage and intercell interference, and the Quality of Service (QoS) or data rates of the users. This is implemented by using a fast inner power control loop and an outer rate control algorithm, working on a slower time scale.

Demand-Responsive Pricing in Open Wireless Access Markets

Radio resource management (RRM) across operator boundaries is emerging as a salient feature for wireless systems beyond 3G. Until recently, research has been confined to solutions where cooperating networks enter explicit sharing agreements that define how responsibilities and revenues should be divided. An alternative would be to share the infrastructure implicitly by establishing an open wireless access market wherein networks not only compete for users on a long-term time-scale, but also on a much shorter time-base. This could be realized with an architecture where autonomous trade-agents, that reside in terminals and access points (APs), manage the resources through negotiations. In this paper we develop a framework for studying demand-responsive pricing in contexts where APs with overlapping coverage compete for users. Resources are partitioned through a proportional fair divisible auction and our aim is to establish if, and when, an open market for wireless access can be self-sustained. Compared to a scenario where APs cooperate, our results show that, an open access market results in better services at lower price which in the prolonging also yields more satisfied customers. As an effect demand will increase and, from the perspective of the APs, act as a counterbalance to the reduced prices. Thus, the revenue earned by the APs will be comparable to the one in which obtained through AP cooperation and monopoly (cartel) pricing. Generally speaking, the difference between the cooperative and noncooperative RRM is small when the demand is concave and increases with the convexity of demand.

LTE and HSPA for fixed wireless broadband: Datarates, coverage, and capacity in an Indian rural scenario

Fixed wireless systems are candidate solutions to connect billions of users not yet connected to the Internet. In this paper the capabilities of HSPA and LTE fixed wireless systems in terms of coverage, datarates, and capacity are discussed and evaluated. Results indicate that in an Indian rural scenario with an inter-site distance of 40km, monthly data volumes of 200MB per user together with a cell-edge datarate of 5Mbps are supported by HSPA on 10MHz (downlink, 1×2). For LTE monthly volumes of 430MB per user are reached in both downlink and uplink, together with cell-edge datarates of 5Mbps in downlink and 2Mbps in uplink. A key enabler is the use of directional rooftop terminal antennas.

Congestion-Based Rate and Power Control in Wireless Cellular Networks

In a cellular network it is necessary to make a trade-off between congestion and Quality of Service (QoS) of the users. To ensure good system performance in uplink of a WCDMA network, control loops are used to adapt to changing radio and interference conditions. A fast inner power control loop updates the transmission powers of the mobiles based on measurements related to QoS, which are compared to a reference value. The reference value is set dynamically by a slower outer rate control loop that uses measurements of congestion. There is a time-scale difference between the loops, but joint dynamics cannot be neglected. In this paper we derive a high order system model with distributed feedback control based on locally measurable information. We model the time-scale difference between the loops and include this in the model. We give sufficient conditions for stability using control theoretic methods and validate the model and results by simulations.

Distributed Demand-Aware Access Selection in Wireless Multi-Cell Data Networks

Regardless of advances in transmission technology, wireless broadband access will result in that fewer active users can be supported in a given cell. This may, due to lower levels of statistical multiplexing, yield in an unbalanced network. For such contexts load aware access point (AP) selection (load balancing) has been proposed as a means to increase network performance. This paper evaluates the downlink capacity (maximum number of users that can be admitted given a throughput requirement) of distributed load aware AP selection criteria for a well planned network, where the expected number of users per cell coincide. We propose a market based algorithm in which AP selection is aided by market mechanisms. In contrast to most of the existing research, we account for that interference levels generated in different cells depend on user assignment, and therefore varies as terminals perform handoff. Compared to single-frequency systems where users base their selection on the received signal strength our results show that the downlink capacity can be increased with around 25 percent by introducing a channel plan in combination with demand, or load, aware AP selection criteria. This gain is fairly insensitive to the throughput requirement and does not come at the expense of uplink performance. To benefit from demand metrics it is, however, of paramount importance that the entire system bandwidth is not reused in all cells.