With exploding demand for mobile broadband services, networks must evolve to meet expanding capacity and coverage demands. Small cells are emerging as a viable technology. This paper reviews how backhaul for small cells will need to adjust to meet the specific challenges for small cell deployment.
Errol Binda, Senior Solutions Marketing Manager for Aviat Networks, discusses the recent Aviat Networks and Symmetricom, Inc. announcement with Manish Gupta, VP of Marketing for Symmetricom, Inc, and Shaun McFall, Chief Marketing Officer for Aviat Networks at CTIA 2011.
The beauty of IEEE 1588v2 (i.e., Precision Time Protocol) synchronization is that it is a bookended solution. In theory, there is no need to worry about what is in between or underneath—from a Layer 1 transport perspective. While in principle this is accurate, there are a couple “unique” aspects of running 1588v2 over a microwave network that should be carefully considered in your deployment plans.
First, the infamous “last mile” is in reality typically many miles across multiple microwave radio hops—which may consist of a mix of linear, ring and hub-and-spoke configurations. Unfortunately, more hops introduce more packet transmission delay and delay variation over the backhaul—a potentially lethal mix for sync transport—the amount of which is proportional to the number of microwave hops. Careful design and engineering are required. On a bright note, Aviat Networks and Symmetricom recently validated <1.5ms delay could be achieved across 10 hops—well within the requirements for mobile backhaul.
Second, most advanced microwave systems now support Adaptive Coding and Modulation (ACM), a key benefit for microwave transport that allows the effective throughput of the microwave link to be dynamically changed to accommodate for radio path fading, typically due to changes in the weather. If bandwidth is reduced as a result of an ACM change, it is critical that advanced traffic and QoS management techniques be applied in the microwave systems to ensure that 1588v2 traffic (packets carrying timestamps) are given the highest/strict priority for transmission, and are not subject to delay or discard. On a brighter note, Aviat Networks and Symmetricom recently validated that 1588v2 could operate over a highly loaded (approaching 100 percent) microwave network running ACM.
In a nutshell, there are some unique considerations for running 1588v2 over microwave – but the outcome can be predictably bright with proper engineering.
Check out the Aviat Networks application note for more information on the Aviat Networks/Symmetricom partnership and 1588v2 network synchronization over microwave backhaul.
Errol Binda
Senior Solutions Marketing Manager, Aviat Networks
Based on microwave Total Cost of Ownership (TCO) model posted earlier, the most significant contributor to total cost is ongoing OPEX.
We see an increasing trend of operators making decisions on backhaul solution based mostly (sometimes solely) on price (or initial CAPEX). While initial CAPEX is important, if the goal is lowest cost, this can be problematic approach as initial CAPEX it is not the most significant contributor to total cost. Ongoing OPEX is key.
Perhaps a better approach would be to focus on features most impacting lowering total costs. For instance, adaptive coding and modulation can lower antenna sizes – which can reasonably reduce 10 year TCO by as much as $48,000 (which is 2-3x more than initial CAPEX). Deploying ring architectures with high layer (L2/L3 or packet-based) failure recovery techniques can enable lower per hop reliability and smaller antennas – further lowering costs.
Gary Croke
Product Marketing, Aviat Networks
Martyn Warwick from Mobile World Congress 2011 in Barcelona, Spain, on the growth of wireless backhaul transmission traffic. As mobile operators ramp up 3G and begin to transition to 4G, Kissner says that microwave backhaul is well positioned to service data and voice communications traffic needs for the foreseeable future.