Marija Malnar

Comparison of ETX and HOP count metrics using Glomosim simulator

Routing protocols for wireless mesh networks (WMN) are traditionally focused on finding paths with the minimum hop count. In WMN the main goal is to achieve as the best possible quality and efficiency of data transmission between source and destination nodes as possible. To achieve such transmission, different parameters (power consumption, packet loss, delay, etc.) influencing data transmission need to be optimized. A routing algorithm should select better paths by taking the quality of wireless links into account. In this paper performances of two routing algorithms ETX (expected transmission count) and HOP count metric are analized and compared. Simulation results are obtained from practical implementation of ETX metric in Glomosim simulator.

Novel power-based routing metrics for multi-channel multi-interface wireless mesh networks

In this paper the problem of selecting optimal paths in a MCMI (Multi-Channel Multi-Interface) WMN (Wireless Mesh Network) is considered. The WMNs are characterized by high dynamic range of the received signal level, especially in the indoor environment. To improve the existing routing metrics and track fast changes that occur in the link state, a corresponding parameter based on the received signal level was assigned to each link. By combining this parameter and known metrics, ETX (Expected Transmission Count), WCETT (Weighted Cumulative ETT) and MIC (Metric of Interference and Channel-switching), three new metrics were formed. All metrics were incorporated in MCR (Multi Channel Routing) protocol and an appropriate propagation model was used for simulations in a real, indoor environment. Proposed metrics, original metrics, MCR protocol, and indoor propagation model were implemented in Glomosim simulator. New metrics were compared against known metrics and also among each other in terms of throughput of user data and average end-to-end delay of the network. The results have shown that proposed metrics significantly outperform original metrics. With this approach, better network performance can be achieved without any additional hardware and with minimal software changes.

A new quality of service aware multi-channel multi-interface link layer protocol for wireless mesh networks

Abstract A new link layer protocol, quality of service hybrid multi channel protocol (QoS–HMCP), that takes into account the need for QoS support in multi-channel multi-interface wireless mesh networks (MCMI–WMNs) is proposed in this paper. QoS–HMCP protocol retains most properties of enhanced distributed channel access (EDCA) mechanism, defined by the 802.11 standard, as well as the basic mechanisms of HMCP protocol. To achieve good network performances with QoS–HMCP protocol in MCMI network, it was necessary to precisely define the channel coordination and procedure for the medium competition of EDCA functions (EDCAFs) after the expiration of interval of time within which a particular EDCAF has the right to initiate data exchange sequences onto the wireless medium—transmission opportunity. Taking into consideration the previously defined conditions, four versions of QoS–HMCP protocol are proposed in this paper. These versions were compared with each other and with basic HMCP with regard to the throughput of user data and delay through the network. The four versions of the QoS–HMCP protocol, multi channel routing (MCR) protocol and chosen metric were implemented in Glomosim simulator. The results have shown that implementation of QoS–HMCP protocol in MCMI–WMN resulted in a very small delay for voice and video traffic, while low-priority traffic categories (best effort and background) were still able to access the media.

An analysis of performances of multi channel routing protocol based on different link quality metrics

In this paper performances of the Multi Channel Routing (MCR) protocol are analyzed. This is a protocol for multi-channel multi-interface wireless mesh network (WMN), so it must have a certain channel switching algorithm. The main goal of the routing protocol in WMN is to achieve the best possible quality and efficiency of data transmission between the nodes in the network. Because of that, different parameters have to be included in the calculation of link cost (link metric). In the paper different link metrics which MCR routing protocol could use are described and compared, taking into account throughput and delay through the mesh network. These metrics are: ETX (Expected Transmission Count), ETT (Expected Transmission Time), MIC (Metric of Interference and Channel-swhiching and WCETT (Weighted Cumulative ETT) metric. In addition, to get as real results as possible, link quality between two nodes was calculated using the indoor propagation model. Simulation results are obtained from the practical implementation of MCR routing protocol, for each of these metrics and real indoor propagation model in Glomosim simulator.

Optimization of routing protocols and metrics for multi-channel multi-interface wireless mesh networks

One of the main goals of this paper is to improve the existing routing metrics in such a way to track fast changes that occur in the link state. Three new metrics are proposed by introducing a parameter based on the received signal level into three known metrics. The results have shown that proposed metrics significantly outperform original metrics. Moreover, a new link layer protocol, Quality of Service Hybrid Multi Channel Protocol (QoS-HMCP), that takes into account the need for QoS support in multi-channel multi-interface Wireless Mesh Networks (MCMI - WMNs) is proposed in this paper. The results have shown that implementation of QoS-HMCP protocol in MCMI-WMN results in a very small delay for voice and video traffic, while low-priority traffic categories were still able to access the media.

A method for elimination of phase jitter in software signal demodulation

This paper describes a new method for phase jitter elimination. It is based on detection of signal passing through zero after demodulation, which helps to determine a residual carrier frequency, and subsequently phase jitter elimination. Classical ways of phase jitter elimination require a frequency search in some range, while this new method is much faster. The method is implemented in the software for offline analysis of modulation quality for 16-QAM signal constellation. It analyzes the signal at receiving IF of radio-relay device. The program consists of several separate functional units, which are described in text. Measurements were made on real signal under the laboratory conditions.