We Want It Now – Access to Mobile Apps That Is
How one technology may help to keep costs down while keeping up with the demand and strain on our existing networks
By: Frank Rayal
May. 4, 2011 02:46 PM
At Starbucks, Panera, and McDonald's restaurants everywhere, personal hubspots can be purchased to fuel our need to access applications on our mobile devices. Today, we automatically assume that we are able to access applications and the Internet if we have a connection but, with the rapid adoption of smart phones and tablets, will the network be able to handle it? Or will our applications just time out, stall, or take forever to run? Operators are still trying to figure out how to meet the anticipated demand.
One solution to the evolving wireless broadband capacity crunch is a heterogeneous access network composed of macro cells, plus a range of small cell solutions: microcells and picocells, carrier WiFi, and femtocells to add capacity and performance. Wireless operators are starting to implement small cell access solutions; however, adoption has been slowed down due to the lack of cost-effective backhaul solutions.
Currently, mobile backhaul solutions such as microwave and fiber utilize a point-to-point (PTP) architecture where base stations have full utilization of dedicated backhaul bandwidth. PTP is provisioned based on peak volume so during off-peak times the excess spectrum is idle. Point-to-Multipoint (PMP) is the ability to backhaul several base stations through a single backhaul hub by creating multiple links that share the hub bandwidth. PMP backhaul is intelligent, based on sharing resources and is ideal technically and economically for small cell backhaul.
Technically, traffic patterns on small cell base stations are very different than macro cell base stations. Compact, below-roofline base stations such as micro or pico cells use low power and are mounted at low height to avoid the interference of the high cellular towers/macro towers. This means that their coverage area is small. Small coverage area means less interference to adjacent cells and that's why compact base stations provide up to double the capacity of macro base stations. Macro cells have a low peak to average ratio whereas small cells have a high peak to average traffic ratio: on average, there are fewer users served by small cells, but the performance is better (i.e., better download and upload speeds). When a small cells peak, it does so for a very short period of time.
Furthermore, traffic patterns for data services are not as predictable as those of voice networks. For example, voice networks have busy hours that typically happen at known times during the day where subscribers drive up the traffic on several base stations at the same time. This is different in data networks where traffic patterns are not predictable: data consumption can happen at any time and is different between base stations.
Based on the described traffic patterns, it would be extremely inefficient to dedicate bandwidth to each compact base station independently, especially if the dedicated bandwidth is designed to match the peak traffic performance which can only be achieved for very brief moment with small cell architectures. Given that peak traffic on any base station can only occur when network utilization is low - that is when adjacent base stations are not very busy - it becomes advantageous to use PMP backhaul.
In this case, a number of base stations share the bandwidth, which is fine given that they don't peak at the same time and, if they do, only for very brief period of time where traffic on adjacent base stations is low. PMP configuration is made more efficient by using "dynamic bandwidth allocation," which shifts resources from a base station with low traffic requirements to one with high traffic demand. This enables optimization of bandwidth to serve the base station with highest traffic requirements at any particular moment in time.
Economically, PMP backhaul with dynamic bandwidth allocation makes sense. Backhaul spectrum is conserved, which reduces costly spectrum costs. Less hardware is required at the hub site with a single hub module serving multiple remote base stations. And the solution is intelligent, requiring very little human intervention. This translates into significantly lower capex and opex. For example, backhauling four compact base stations in PMP configuration results in 38% less total cost than an equivalent PTP configuration.
Advances in PMP backhaul technology can now help operators eliminate urban hotspots by helping them quickly double their capacity, at 50% of the total cost of ownership of fiber PTP solutions. Subscribers will be able to use their applications when they want to without experiencing delays. This will keep mobile users happy and operators will be able to avoid subscriber churn.
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