Karol Kowalik

RARE - Resource Aware Routing for mEsh

An important element of any routing protocol used for wireless mesh networks (WMNs) is the link cost function used to represent the radio link characteristic. The majority of the routing protocols for WMNs attempt to accurately characterise the radio link quality by constructing the link cost function from the measurements obtained using active probing techniques, which introduces overhead. In this paper we propose a new approach called resource aware routing for mesh (RARE) which instead employs passive monitoring to gather radio link information. This results in a smaller overhead than the other methods that require active network probing, and is load independent since it does not require an access to the medium. Moreover, we show that our RARE approach performs well in a real radio environment through a number of experiments performed on a static 17 node WLAN mesh testbed.

Practical issues of power control in IEEE 802.11 wireless devices

Power control techniques for IEEE 802.11 wireless networks have already gained much attention. Such techniques are particularly attractive because they can improve various aspects of wireless network operation such as interference mitigation, spatial reuse in dense wireless deployments, topology control, and link quality enhancement. However, until recently implementing such advanced power control using off-the-shelf wireless devices was not considered possible. For example, Abdesslem et al. [1] stated that ldquomany novel power control solutions cannot be efficiently implemented over existing IEEE 802.11 cardsrdquo. However, in this paper we demonstrate that power control is now feasible and can be implemented in current IEEE 802.11 cards with per-packet granularity and low power switching latency.

Making OLSR Aware of Resources

An important element of any routing protocol used for Wireless Mesh Networks (WMNs) is the link cost function used to represent the radio link characteristic. The majority of the routing protocols for WMNs attempt to accurately characterise the radio link quality by constructing the link cost function from the measurements obtained using active probing techniques which introduces overhead. In this paper we present a modified version of the Optimized Link State Routing (OLSR) protocol which uses the link cost function values provided the Resource Aware Routing for mEsh (RARE) module which employs passive monitoring to gather radio link information. This results in a smaller overhead than the other methods that require active network probing and furthermore is load independent since it does not require an access to the medium. We demonstrate the necessary modifications to OLSR required to make it work with RARE. The results of our ns-2 simulations show that such a combination (OLSR + RARE) performs well over various wireless topologies.

MeshScan: Performance of Passive Handoff and Active Handoff

A core problem of fast handoff is when handoff should perform and which Mesh Node (MN) should associated with. We have developed a fast handoff management scheme called MeshScan to provide a novel use of channel scanning latency, by employing open system authentication in both Passive Handoff and Active Handoff. This scheme comprises three steps: firstly a client device takes advantage of the Wireless Mesh Network (WMN) architecture to maintain a list of active MNs. Secondly MeshScan Handoff Sensor performs handoff when it receives a disassociation management frame from the serving MN or when the measured signal strength from the serving MN exceeds a given threshold. Thirdly when handoff is required, a client transmits Authentication Request frames to all MNs from the list instead of broadcasting Probe Request frames, as in an active scan to discover the available MNs. The handoff delay is used as criteria for system performance. Numerical results are presented to demonstrate the feasibility of MeshScan with Active Handoff algorithm. This fast handoff scheme is feasible by upgrading the software only on the client side. This paper compares the theoretical handoff latency of MeshScan with other approaches and we demonstrate the effectiveness of our scheme through experiment.

Experimental Measurement of Overhead Associated with Active Probing of Wireless Mesh Networks

Wireless Mesh Networks (WMNs) represent the next generation wireless networks. The increased capacity of WMNs means that they are now capable of providing backhaul services traditionally maintained by wired networks. The attraction of WMNs is their ease of deployment and ability to self organise, self configure, and self heal. In order to successfully achieve this objective careful consideration must be applied when constructing a WMN. In order to optimise the operation of the network, data should traverse the network by means of the most efficient route. Characterisation and path selection will be determined by the routing algorithm coupled with the link cost metrics. In this paper we experimentally investigate the overhead associated with the estimation of the link quality using the Estimated Transmission Time (ETT) metric.

Conservative Transmit Power Control Mechanism for 802.11 Mesh

Power control techniques for IEEE 802.11 wireless networks have already gained considerable attention. Such techniques are particularly attractive because they can improve various aspects of wireless network operation such as interference mitigation, spatial reuse in dense wireless deployments, topology control, and link quality enhancement. In this paper we propose a novel delivery ratio based Conservative Transmit Power Control (ConTPC) mechanism. Our implementation is conservative when it comes to deciding if the transmit power should be reduced for a given link. This is because we do not want poor quality wireless links to further reduce their quality and be overwhelmed by other links transmitting at maximum power. We have experimentally evaluated the benefit of the proposed power control scheme when compared with fixed power level systems. We show that our ConTPC mechanism can increase the throughput, however the magnitude of this enhancement largely depends on the topology of the wireless network.

MeshScan: fast and efficient handoff in IEEE802.11 mesh networks

Handoff delay is one of the major problems in Wireless Mesh Network (WMN) that needs to be solved in order to allow time-critical and real-time applications run continuously during handoff. We have developed a fast handoff scheme called MeshScan to provide a novel use of channel scanning latency by employing open system authentication. This scheme comprises two steps: firstly a client device takes advantage of the WMN architecture to maintain a list of active mesh nodes. Secondly when handoff is required, a client transmits Authentication Request frames to all mesh nodes (MNs) from the list instead of broadcasting Probe Request frames as in an active scan to discover the available MNs. This fast handoff scheme is feasible by upgrading the software only on the client side. This paper compares the theoretical handoff latency of MeshScan with other approaches and we demonstrate the effectiveness of our scheme through experiment.

Scenarios for 5G networks: The COHERENT approach

Efficient coordination among network elements and optimal resource utilization in heterogeneous mobile networks (HMNs) is a key factor for the success of future 5G systems. The COHERENT project focuses on developing an innovative programmable control and coordination framework which is aware of the underlying network topology, radio environment and traffic conditions, and can efficiently coordinate available spectrum resources. In this paper, we provide a set of scenarios and use cases that the COHERENT project intends to address.

Application of the CBRS Model for Wireless Systems Coexistence in 3.6–3.8 GHz Band

In this paper we discuss the results of the experiment conducted in Poznan, Poland, where the performance of CBRS spectrum sharing model in 3.6–3.8 GHz band has been verified. Three-tier model has been tested, where the highest priority has been assigned to the fixed WiMAX users, whose transmit parameters cannot be modified. Second tier of users was constituted by the peer-to-peer microwave line, whereas the third tier of lowest priority covered the low-power cognitive small-cells. The whole system has been managed by the dedicated remote database located in Finland. Experiments have been carried out in the laboratory, where mainly the functionality of the management of the third tier user has been tested, while protecting the users assigned to two higher tiers.