Wireless Municipal Mesh Networks

Municipal Mesh Networks, also known as muni networks are another wireless platform that promises to support the delivery of IPTV services to end users. A number of these network types have been deployed in various cities and towns around the world.
FIGURE 2.11 Municipal mesh network architecture Municipal networks operate in an outdoor environment in either the unlicensed 2.4 or the 5 GHz spectrum range. Wi-Fi, also known as the 802.1x family ofwireless products has been the technology of choice for building mesh networks,because most if not all notebooks and handhelds manufactured nowadays comewith in-built Wi-Fi interfaces. Constructing Wi-Fi networks in an outdoor environment requires the use of a number of access points interconnected to each other and to a wired connection that provides backhaul to the broadband service provider (Fig. 2.11).
Mesh Wi-Fi Access Points (APs) APs used by municipal networks cover a much greater area compared to conventional indoor APs. They are generally attached or mounted onto fixed physical structures that provide a goodline of sight and easy access to power. Suitable locations for mounting outdoor APs include light posts, tall buildings, and communication towers. Interconnecting outdoor APs back to a central point using some type of physical cable is cost prohibitive for most deployments. Therefore, all APs in a municipal wireless networking architecture dynamically connect wirelessly with each other and a gateway AP in a cluster type configuration. The gateway aggregates the 802.11xsignals within the cluster and interfaces via an Ethernet port with the broadbandbackhaul link. The number of APs in a cluster varies between implementations.
Each AP in the cluster is ruggedized and uses a mesh routing protocol to interconnect with other APs and back to the backhaul point of presence. The main responsibility of the routing protocol is to provide the most efficient route for IP packets through the mesh from each AP to and from the backhaul link. It does this by continuously monitoring the wireless network and identifying wireless paths that provide the greatest bandwidth throughput capabilities. Mesh APs come in two variants single and multiple radio configurations:

. Single Wi-Fi radio-mesh APs use one channel to support access from various client devices in addition to carrying interconnectivity traffic to and from the mesh network. To minimize constraints and improve performance, these types
of APs are typically configured into clusters that operate at different frequencies to their neighboring clusters.

. Dual Wi-Fi radio-mesh APs use separate channels for carrying mesh traffic and providing access to client Wi-Fi devices in the 2.4 GHz frequency band.
The use of two separate channels that operate in different frequency bands offer improved performance levels and reduced latency levels that make dual channel APs more suitable to carrying time-sensitive applications such as IPTV.

Wired Backhaul Connectivity A wired backhaul is required to provide connectivity to the IP data center and onwards to the public Internet. A technology called virtual LANs (VLANs) is often used to segment the different types of traffic that traverse a wireless municipal network. Note that VLAN technology will be described in greater detail later in the book.
At the time of writing the average downstream data rate of a municipal wireless network is approximately 1 Mbps, which is more than adequate for public Internet access applications. However, IPTV has more demanding throughput needs, therefore, deployments of video centric applications over these types of networks are typically confined to specialized functions such as streaming IPTV content from Wi-Fi cameras.