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Defining the Layers of Wireless Ethernet -- also known as Mobile Broadband
by Erik Boch, CTO & VP of Engineering
12/8/2008
Wireless Ethernet, or Mobile Broadband is a term often associated with the deployment of next generation mobile networks … so called"4G" mobile networks. These networks will have the capability to deliver advanced, broadband services to both fixed and mobile users throughout the service area.
As shown in Figure 1, mobile networks are typically designed in"layers". In order to implement these broadband functionality to enable the associated mobile data services, there are a number of contributing layers of the network that also must equally be"broadband" capable.
First, at the edge of the network is the end-user device …. Or"Smart Phone". These devices have evolved from their voice legacy to have capabilities akin to their laptop and tabletop computer cousins. In order to realize their potential, they require high capacity connectivity to the rest of the network.
The number of end-user devices being deployed is expected to see continued explosive growth. Over 5B mobile subscribers are expected globally by 2013 (source = Informa Telecom and Media, June 2008). In addition to the growth in the"traditional" cellular domain, new, broadband access technologies are also entering the market as mobile broadband enablers and are expecting to also see explosive growth. WiMax in particular is expected to ship over 1B CPE devices and over 15M base stations in 2009 (source = Skylight Research)
The network layer which connects the end-user to the local base-station is the wireless access layer …. Or "Last Mile". The candidate technologies for the implementation of broadband capability in this layer of the network are LTE and WiMax. Both of these have the capability to deliver the necessary bandwidths. Both of them in turn rely on broadband Ethernet connectivity from the next layer of the network … the backhaul layer.
These"mobile broadband" access layer technology solutions are expected to fuel impressive growth curves through the addition of a wide range of new services. These services take many forms … some of which we don't even know about yet (!) …. But they share a common need for continuously increasing bandwidth.
The increases in bandwidth available to the mobile-user layer can be seen through a compilation of the capabilities of the various deployed access technologies that have been made available over the recent years in response to market demands. The key candidate technologies that are being deployed in support of mobile broadband are LTE and WiMax. LTE (Long Term Evolution) is a broadband enhancement to GSM-based mobile cellular deployments and WiMax is a new mobile broadband technology based on IEEE 802.16e.
Supporting this trending toward IP/Ethernet is a similar trending toward IP/Ethernet in the transport (backhaul) layer. This is consistent with the escalation in broadband, data-oriented services to the mobile user community. This data is inherently connectionless, Ethernet-based in nature and therefore the most efficient transport technology is also [similarly] Ethernet based.
The next layer of the network (see Figure 1), the backhaul layer or "middle mile" of the network is an often over-looked part of the overall broadband functionality within the network. Traditional use of T1 or E1 circuits to construct this layer in legacy voice-based mobile networks will no longer suffice in these newer"4G" networks …... broadband Ethernet technology is required.
There are two candidate technologies for the implementation of broadband Ethernet backhaul … fiber optics and Wireless Ethernet. Fiber optics is not normally available and is costly and time consuming to deploy if unavailable. Wireless Ethernet backhaul on the other hand is cost effective and rapidly deployable. Additionally, it can equally serve within the dense downtown city core as well as the suburban fringe and rural regions within the network.
Figure 2 shows the relative growth/decline of the various backhaul technology solutions. As expected the switched-circuit-centric solutions (T1/E1, SONET …. or"PDH/SDH") are declining due to their applicability to low speed, switched network implementations. Microwave and optical Ethernet are increasing, with microwave deployments being the prominent of the two.
A typical metro broadband mobile Ethernet network can be constructed using established cellular coverage methodology. As shown in Figure 3, the cells are then connected using high bandwidth, highly scaleable microwave Ethernet backhaul radio systems. The microwave backhaul is typically designed using constrained-mesh or ringed sub-circuits to optimize network resilience and availability. A number of these microwave sub-circuits is typically employed to attain a complete metro network coverage solution. Normally a small number of fiber points-of-presence (PoP) are employed to connect to the fiber metro core layer. Typically, these networks are designed to scale from 100's of Mbps of aggregate traffic to several Gbps of aggregate traffic (sustained, full duplex) through software-based up-speeding implemented on a"pay as you grow" basis.
Summary
Broadband"4G" mobile network deployment success will rely on both the latest, most advanced handsets and a highly capable supporting network infrastructure. Broadband wireless Ethernet backhaul radios are now, and will continue to be, vital building blocks in the broadband backhaul layer of these networks.
About the Author
Erik Boch holds a Masters degree in Electrical Engineering from Carleton University in Ottawa and is a registered professional engineer. Erik has held senior engineering or technical management positions at a number of communications and aerospace companies namely Litton Systems, ComDev, Lockheed Martin and Alcatel Networks (formerly Newbridge). While at Alcatel, Erik was AVP of the Wireless Systems Group and was involved in various aspects of microwave & millimeter wave subsystem and system design for more than 22 years. Erik led the R&D team at Alcatel (formerly Newbridge) that introduced the first ATM-based Fixed Wireless Access System in the industry.
About DragonWave
DragonWave designs, markets and supports broadband, wireless networking products for service providers and enterprises requiring reliable, predictable, interference-free, high-bandwidth transmission of real-time, IP applications. DragonWave products meet the demands of a wide range of applications as well as delivering a value proposition that enables operators and service providers an "invest as you grow" capability that leverages profitable growth. DragonWave is headquartered in Ottawa, Canada's high-technology capital.
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