Orange and Vodafone have done it, 3 and T-Mobile have done it. Even educated tier two operators will soon be doing it. Although cost saving is the attraction, network sharing brings its own challenges – forcing engineers to meet the technical and business priorities of at least two competing operators. Shirin Dheghan and Nick Cooper share this network space to outline the challenges and potential solutions.
One of the main expenses incurred by wireless operators is the operational cost associated with base station sites including rent, backhaul transmission and maintenance. Operators are constantly looking for ways to maintain and improve the coverage and quality of existing networks, whilst simultaneously ensuring that CapEx is kept under control. Network sharing is becoming an increasingly popular option for many service providers as a way to cut costs whilst accelerating ubiquitous coverage and high data rates. This brings a whole new set of challenges to the wireless industry. The task of bringing together two networks with legacy software, databases and processes requires new automated tools focused on network sharing. Such tools need to easily interface to individual operator's legacy systems and combine this data to optimise the shared network to maximise savings and service quality whilst serving two operators with potentially competing business objectives. Adoption of such tools is a vital step in achieving savings of 20% predicted by operators.
At first glance, the task of combining or optimising two networks into a "shared network" appears little different from the task of optimising a single network: An engineer will have a set of sites -both existing and potential candidates- and will have choices to configure those sites to provide an optimum level of service. They may have a budget to make changes and information concerning the capital costs of different changes they may make to this network. They may also have information on the ongoing operational costs of each component. The engineering task is to make the network decisions that result in the most profitable delivery of this service (balancing the revenue consequences of these decisions, if any, with the associated capital and operational costs). However, with a little closer inspection, network sharing becomes a more involved and complex task than first considered. This article discusses some of the factors that fundamentally change the process of optimisation in order to "share" networks.
Sharing resources allows overlapping and redundant equipment to be removed and then allows the cost of the remaining resources to be divided among the network operators. The benefits of sharing will depend on the extent to which network resources are to be shared and this in turn will determine the complexity of the engineering task. At one end of the scale the exercise may be only to share site locations and to maintain separate equipment for each operator. At the other end operators may choose to combine resources right through to antennas, cabling, base station and transmission equipment. The design approach will clearly differ according to what items are combined and what are kept separate. At the very least the scope of the sharing exercise will define whether engineering will be designing a single network or multiple networks.
It is important to stress one factor that is often overlooked in traditional engineering situations and tools: Sharing a network is all about the money. The primary reason for sharing networks is to reduce capital and operational costs while maintaining an acceptable level of service. This requires engineering teams to understand costs in much greater detail than they may be used to. Within a single operation, costs can often be pushed into the background as far as engineering is concerned. Engineers will of course spend money while performing their operational and maintenance activities but usually this spend is disconnected from the budgetary aspects of network operation. However, costs have to come to the fore as soon as there are multiple organisations involved. If the engineering objective is to re-design networks so that each operator benefits from continued service at reduced costs, then a balance of benefits has to be maintained for all operators. Engineering teams must hence justify their decisions to all operators and those justifications will have to be in terms of financial benefits versus the costs involved.
For a network sharing exercise to be successful, the design and engineering teams must understand the scope of changes that they can make. Then they must maintain details of the financial impact for each of the possible changes. Subsequent decisions must then count the cost of all the changes proposed and ensure that the financial impact of those changes can be calculated.
Competing point of view
A need for separation between sharing operators introduces another new concept for network design: engineers must maintain an appropriate "Point of View" for each operator. Operators will offer their existing networks into a network sharing agreement and their existing resources will be seen to the other operators as ‘potential resources'. So, the costs and benefits of using any one resource will differ for different operators.
For example, consider a case where Operator A owns a particular site on which Operator B may place equipment. Operator B will see that site as a ‘Candidate' and can choose to use it themselves. If they choose to use the site they will incur a capital cost to install equipment and will then incur ongoing operational costs. At the same time, Operator A sees the same site as an ‘Existing' site and can choose to decommission it if they wish. If they do so they will incur a capital cost to take equipment away but will gain the value of that equipment back again and they will lose the burden of operational costs. In other words for the same site, the cost-benefit issue for Operator A is different from the cost-benefit issue for Operator B. The site has to be seen both from the point of view of A and from the point of view of B at the same time.
To further complicate matters in our example; if Operator B chooses to join Operator A on the site, then the cost model for Operator A will change even though they have not made a change to their network. In the simplest terms the operational costs for the site itself will be shared so both Operators A and B will benefit from Operator B's action. This makes it clear that the engineering teams must consider all the possible permutations as well as operators' points of view when designing the shared networks.
Network sharing introduces some more practical problems for the engineering team. Operators will accumulate extensive amounts of data about their own network over time and they will develop data sets, file formats and working practices that are unique to their own operation. When it comes time to design a shared network the engineering team will be given two or more different sets of data in probably very different formats and derived from very different design and operational methods. The team will require a single model of the shared network so they will be tasked with merging these several sets of data together. They will clearly need tools that can support the various data in all forms and they will need to know how to relate the two sets of data together. This task will be somewhat easier if only the sites are to be shared (and the equipment kept separate) but the intention to share equipment will make this process substantially more complex.
Site selection
A further practical problem is introduced by the fact that the shared design requires site selection. When optimising a single, mature network, engineers do not often have to deal with the consequences of turning off a site. For network sharing however, the intent is to turn off and potentially redeploy upwards of half of the sites that are currently operational. Engineers must therefore think of the non-radio components of the network and the impact that changing network topology will have.
For example, a network may rely on sequences of microwave links to fulfil the backhaul transmission between base stations and the switching centres. Network sharing might lead to some of the intermediary sites in a microwave chain being decommissioned which might break the transmission links for some sites elsewhere. In a similar example, co-locating equipment from multiple operators will greatly increase the volume of data flowing from a site. The cost of managing the increased transmission might outweigh the savings made from co-locating in the first place. This forces the operating teams of shared networks to have the capability to perform end to end optimisation.
Site Selection issues are not confined to the transmission system. As another example, placing two operators' infrastructure at the same site location will increase the burden on the mast placed at the site. It may be that a site is prohibited from adding additional antennas (for example due to weight or wind loading limits or to planning regulations.) This restriction might mean that site sharing can only be performed if antenna sharing is also performed. However, the sharing of antennas may compromise service quality due to the fact that height, azimuth, tilt and other physical parameters have to be linked.
These situations can be worked through but they require new tools and capabilities within the engineering team that can look beyond the normal air interface considerations of optimisation. Engineers need tools that can incorporate the physical and logical limits on a network; that can factor in the costs of reaching or breaching those limits; that can understand the links that will form between resources as they are shared and that can understand the cost implications of making and breaking those links.
As a final point, all of the issues above will be further compounded by the choices of radio technology. What if the shared networks are to offer multiple radio technologies? What if the original networks offer different subsets of the available technologies? It should be noted that operators may have already performed a type of network sharing exercise when they chose to co-locate 3G equipment on their own, pre-existing 2G sites. However, 2G to 3G migration was still confined to a single operator experience. The challenges of network sharing between operators are far more complex in both financial and engineering terms. However; savings in excess of 20% are certainly possible within a shared network so the investment should be well worthwhile.
Shirin Dheghan is ceo Arieso, Nick Cooper is an Arieso product manager.