April 6, 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.
Senior Solutions Marketing Manager, Aviat Networks
March 30, 2011
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.
Product Marketing, Aviat Networks
March 16, 2011
When choosing the right backhaul technology, total cost of a microwave system is a critical, often overlooked, consideration. TCO is not widely understood today. Lack of understanding of microwave TCO can lead to poor decisions about choice in backhaul technology and obscure the relative importance of features. Features that lower critical components of TCO are often not given enough attention.
A summary of a TCO model for a mobile operator in North America is shown below. Clearly, ongoing OPEX resulting from tower leases represent largest contributor to total cost. These lease costs include tower space for antennas and cable runs, shelter/cabinet space and power, and ongoing move/add/change fees regularly paid to tower companies. The largest portion of this tower lease is related to the antenna size. Microwave products and features that enable smaller antennas sizes, less indoor space, and fewer cables are most important for operators.
*Note: for private network applications (like state/local governments, public safety organizations, and utilities) who generally own towers, initial CAPEX is often higher, leading to an overall reduction in ongoing OPEX and TCO.
Make sure to check back next week for post #2 ” How Important is Initial CAPEX?” where I breakdown the true costs of initial and ongoing CAPEX.
Product Marketing, Aviat Networks