Marina Petrova

Performance study of IEEE 802.15.4 using measurements and simulations

IEEE 802.15.4 was developed to meet the needs for simple, low-power and low-cost wireless communication. In the past couple of years it has become a popular technology for wireless sensor networks. It operates primarily in the 2.4 GHz ISM band, which makes the technology easily applicable and worldwide available. However, IEEE 802.15.4 is potentially vulnerable to interference by other wireless technologies working in this band such as IEEE 802.11 and Bluetooth. This paper gives a short overview of the IEEE 802.15.4 and carefully analyzes the properties and performance of IEEE 802.15.4 through measurement of the RSSI, PER and run lengths distribution using real off-the-shelf hardware. Furthermore we present simulation results from the evaluation of the IEEE 802.15.4 MAC protocol. Finally, we address the coexistence between IEEE 802.11 and IEEE 802.15.4 and measure the impact these two wireless technologies have on each other when operating concurrently and in range

Interference Measurements on Performance Degradation between Colocated IEEE 802.11g/n and IEEE 802.15.4 Networks

We have made detailed measurements, on the impact of modern Wireless LAN technologies on the IEEE 802.15.4 in the 2.4 GHz ISM band. We have specifically focused on IEEE 802.11g and pre-standard IEEE 802.11n products as potential interferers. Our measurements show that high levels of network traffic interference from either of these technologies has disastrous impact on the performance of IEEE 802.15.4. Our results also indicate that these interference effects are especially difficult to avoid in the (pre-standard) 802.11n case due to the significantly increased channel bandwidth compared to previous Wireless LAN technologies. Widespread adoption of IEEE 802.11n especially in applications involving high data rates (such as backbones for wireless mesh networks) could thus have serious impact on the usability of IEEE 802.15.4 as well as other low-power 2.4 GHz ISM band technologies. This indicates that low-power building automation, consumer electronics and sensor networks may be vulnerable to the interference from the future IEEE 802.11n high-data rate WLAN deployments.

Frequency allocation for WLANs using graph colouring techniques

At present, no standard frequency allocation mechanism exists for wireless LAN access points. In this article, we introduce a number of techniques based on graph colouring algorithms, and demonstrate their effectiveness using simulations. We also suggest a preliminary message format the access points could employ to exchange information regarding the wireless channel and elaborate on the possible protocol architectures that could be used in the actual channel allocation process.

Automatic channel allocation for small wireless local area networks using graph colouring algorithm approach

Classical graph colouring and its generalisations have been used to model various frequency and channel allocation processes in different radio and wireless network contexts for some time now. However, most of this work has targeted cellular networks and graphs with a relatively large number of nodes. In this article we demonstrate how graph colouring can be used as a theoretical basis for a protocol to effectively assign channels to WLAN access points. We also give the outline of the protocol operation, and show its effectiveness with real-life wireless networks.

Wi-Fi, but not on Steroids: Performance analysis of a Wi-Fi-like Network operating in TVWS under realistic conditions

The recent decisions by regulators in the USA and UK to open up unused portions of UHF spectrum for secondary use have been met with keen interest in using these TV white spaces (TVWS) for providing broadband services through Wi-Fi-like connectivity. Amid the ensuing media hype about “Wi-Fi on steroids”, there is a widespread perception that Wi-Fi operating in TVWS will provide much longer range, superior speeds, and more reliable connections than traditional Wi-Fi at 2.4 GHz. In this paper, we present a quantitative analysis of the performance of a network of Wi-Fi-like access points (APs) operating in TVWS in order to obtain a realistic estimate of the achievable range and downlink rate of such a secondary system. Unlike previous studies, we explicitly consider the effects of inter-AP interference and congestion and use real TVWS channel availability estimates from an example region of Germany. We confirm the favourable properties of the lower TVWS frequency range, of enabling better propagation through walls and a larger coverage range for the same power budget. Our results show that operating Wi-Fi hotspots in TVWS might be technologically attractive for outdoor rural areas where user demand is low. However, the extended coverage range in TVWS leads to increased congestion which rapidly limits the system capacity for an outdoor urban deployment with high user density. Therefore, a combined technological and economical analysis is essential before any final judgement can be reached about the viability of large-scale Wi-Fi deployments in TVWS.

Hop-by-hop toward future mobile broadband IP

We try to give some perspectives on likely trends in future wireless broadband networking. The treatment is an exploration of some technologies; due to the requirement to cover the topic from a broad perspective, it is not possible to go into technical details. We review current developments toward future mobile broadband networks, and then present the 4G paradigm of trying to combine heterogeneous networks, both cellular wireless hotspots and sensor networks, together with Internet protocols. We show how different networks play their own roles in the emerging infrastructure so that we can hop by hop wave the broadband network from mobile devices toward the fiber optic core network.

A flexible MAC development framework for cognitive radio systems

Cognitive radios are becoming the technological foundation for efficiently managing the scarcity of wireless spectrum, fulfilling various QoS demands and allowing different networks to coexist. Cognition and spectrum agility in MAC protocols require adaptability and close PHY-MAC interaction. Classically, MAC protocols have been implemented in hardware, which gives a limited possibility for reconfiguration and customization. Recently, software based MAC implementations have emerged although a close hardware-software co-design is typically required to keep the time critical operations in ASICs or FPGAs. We introduce a MAC development framework for enabling fast composition of MAC protocols, which are best fitted to the application requirements, communication capabilities of the radio, and current spectrum regulations and policies. We decompose MAC protocols into their basic functionalities which are perceived as building blocks and are partitioned across hardware/software. Our framework allows on-the-fly realization of the envisioned MAC protocol through wiring of these fundamental components. By exposing extended metadata and hardware functionalities for the MAC implementation through our granular components, together with the support for run-time re-configuration, spectrum agile and cognitive MAC solutions can be easily realized. In this paper, we describe the design rationale and implementation details of our framework on WARP [1] boards. We show through experimental evaluation that the framework provides flexible means for prototyping different reconfigurable cognitive and spectrum agile MAC protocols.

Enhancing cognitive radios with spatial statistics: From radio environment maps to topology engine

Radio environment maps are a promising architectural concept for storing environmental information for use in cognitive wireless networks. However, if not applied carefully their use can lead to large amounts of measurement data communicated over wireless links, causing substantial overhead. We propose enhancing the basic radio environment map concept by spatial statistics and probabilistic models, enabling applications to benefit from environment data while reducing overhead. In this paper we discuss the development of a topology engine, an agent in the CWN collecting and processing spatial information about the environment for storage in the REM. We discuss both technical and architectural issues in enabling such an approach, and outline some of the potential application scenarios for the topology engine.

Full length article: Minority game for cognitive radios: Cooperating without cooperation

In this paper we report on our preliminary results and recent work on building cognitive wireless networks that achieve resource sharing in a local environment. We emphasize two major issues. First, the cross-layer optimization at the network level requires exchange of information between OSI-layers in the terminal and often among the nodes that form the network. Second, the cooperative behavior among the radios is often believed to require a rich exchange of information. We show in this paper that cooperation can be an emergent phenomenon without any complex signalling. We apply Minority Games to cognitive wireless networks to show that resource sharing can be achieved without detailed information exchange or coordination between strategies. We further argue that Minority Games are not only a useful analysis tool, but a potentially efficient method to develop actual resource sharing algorithms. We conclude the paper by pointing out that also other swarm intelligence type of solutions could be applied to cognitive radio communications.

On the scalability of cognitive radio: assessing the commercial viability of secondary spectrum access

We report results from the recently finished QUASAR project, which has studied overall system aspects of cognitive radio technologies and has paid attention particularly to the economic viability of different use cases. We find that successful secondary sharing goes far beyond the detection of spectrum holes. Large-scale commercial success requires that secondary systems are scalable so that a large number of users can be served in an economically viable fashion. Our key finding is that secondary spectrum use is not an attractive method for most of the commercially interesting scenarios, from neither a business nor technical perspective. Perhaps somewhat surprisingly, the likely commercial “sweet spot” for secondary sharing in the lower frequency bands is short-range indoor communications. We also find that regulation does not currently present a significant barrier in Europe or the United States.