Radio Network Sharing – new paradigm for LTE
Network sharing or Radio Access Network sharing between two or more operators will become a reality in near future as ARPU trend decreases, CAPEX(Capital Expenditure)and spectrum costs become speculative. The time is coming when operators have to decide to either evolve or go out of business being swallowed by bigger rivals. The days when a voice centric network paid for itself in time are gone, as the data-centric networks evolve it has to be supplemented with value added services like apps, faster download speeds, etc. Wouldn’t it be wonderful if we could do multiple things with our phones – monitor our home, watch Football, control home appliances, monitor kids, be on top of work email, control our work computers, GPS, do video chat on- demand and all of the above at one flat rate! This is going to be the reality in the next 5-7 years as vendors are looking to provide these services in collaboration with the operators and smart phones.
What does this mean for an operator? More fatter pipes, new investments on hardware infrastructure upgrades, more space, more power and above all more capacity in terms of bandwidth and spectrum. So the path now for an operator would be to either chose the upgrade path or become obsolete. Is there a third way a middle ground that mitigates spending so much for infrastructure investments, well it comes in the form of a sharing agreement, where Operator A shares the network or other resources with Operator B, as pooled resources mean greater reach in terms of capacity and coverage.
Why do we need RAN sharing or for that matter any network-sharing models?
Ironically, there is much talk of an impending spectrum crisis, an alleged shortage of spectrum for cellular networks. A survey commissioned by NSF in 2005 concluded that radio spectrum is underutilized; they found only 5.2% of the spectrum occupied in the range from 30 MHz to 3000MHz. And how can there be a spectrum shortage?
There is a contradiction that the problem at hand is not the lack of spectrum but because it is so inefficiently used. Pockets of spectrum are quite heavily used – for example, the cell phone and specialized mobile radio (SMR) band (a narrow band from 806 MHz to 902 MHz) is 46.3% utilized in New York City; while other bands are barely used at all. Cognitive radios seem like one approach to provide more efficient usage of the spectrum. It might be argued that there is, in fact, not really a shortage of capacity. It’s simply off limits to most users, most of the time. Switch on a cell-phone in most locations in the world and you can see 5-10 different cellular networks, and several Wi-Fi networks. However, most users can only use one of the visible cellular networks, constrained by the contract they are locked into. Nearby Wi-Fi networks are usually off-limits too, because they are secured by their owners.
If we really want to give users access to the abundant wire-less capacity around them, why don’t we make it easier by design and by policy for a mobile client to move freely between the spectrum, and networks, owned by different cellular and Wi-Fi providers? While this approach is clearly counter to current business practices and would require cellular providers to exchange access to their networks more freely than they do today. I believe it is worth exploring because of the much greater efficiencies it would bring; and the much greater capacity that could be made available to end users. Interestingly, a several-fold increase in capacity could be made available for little or no additional infrastructure cost.
Here are some thought provoking ways to increase capacity –
Capacity through more efficient statistical sharing – MNOs tend to heavily over-provision their network in order to handle times of peak load and congestion. Most of the time, the network is lightly loaded. If instead they were able to hand interaction with each other or from cellular to Wi-Fi networks, then their traffic load would be smoother, and their network more efficient. For example, what if AT&T could re-route traffic from their iPhone users to T-Mobile during an overload? Or T-Mobile could reroute their customers’ flows to a nearby Wi-Fi hotspot?
Exploit differences in technologies and frequency bands – Mobile technologies such as EVDO and HSPA provide wide area coverage with consistent bandwidth guarantees; while technologies like Wi-Fi provide high bandwidth and low latency. Lower frequencies provide better coverage and penetration; while higher frequencies provide better spatial reuse. Being able to use the most appropriate technology for the application at hand would make best use of capacity available. For example, a backup where intermittent connectivity is tolerable can be done via Wi-Fi where higher throughput is possible.
Open up new sources of capacity – The ability to move between networks also opens up new sources of capacity. For example, one can now use a network such as that of fon.com to supplement their main network, without having to deploy an extensive Wi-Fi network.
Such crowd-sourcing can be a powerful tool to cover dead spots and relieve congestion. Through mobility across networks, we create a network with heterogeneous wireless technologies by “stitching together” the multitude of wireless networks available today. But the biggest and most significant way to impact networks real-time would be to pool the network resources and use them as needed.
Significant cost savings is the main driver for RAN sharing models. The graphs below illustrate a typical CAPEX/OPEX for developed markets.
Analysis of a typical CAPEX model reveals that a majority of the upfront costs are related to establishing coverage (i.e. access related CAPEX). Approximately 70% of the CAPEX involves acquiring the sites, access equipment, civil works (i.e. construction of the site, installation of the equipment) and laying the transmission network. With 4G, these fundamental implementation issues will be further complicated by the lack of sites, tighter environmental regulations, and health concerns regarding the hazards of radiation. In view of these challenges faced by the license holders, shared network infrastructure solutions need to be explored in order to reduce the financial risks facing the industry, establish faster universal coverage and thus improve time-to-revenue.
Sharing of the network infrastructure will have a significant impact on time-to-revenue because acquisition of sites and deployment resources are scarce and are always on the critical launch path. But more importantly, sharing network infrastructure has long-term CAPEX and Operational Expenditure (OPEX) savings, thus enabling MNOs to focus on developing the applications and services demanded by the marketplace, which will ultimately drive usage, generate revenue, and sustain the overall business case for wireless broadband.
RAN sharing models
For operators there are three different types of decisions to make – go Greenfield, Buy-in or consolidate.
A Greenfield deployment would be the easiest to realize. In this case, two operators jointly agree to build out a new technology (typically 4G). At the outset, the new shared network infrastructure and operations can be based on the capacity and coverage requirements of both operators. The operators would fund the build-out on a 50/50 basis or according to their expected capacity needs.
A buy-in situation arises when one of the sharing operators has already built out a 4G network and is now looking for another operator to share this network. In this case, the second operator would either pay a capacity usage fee or an up-front fee to acquire a share in the network. One challenge in this situation is determining how to agree on potential adjustments and build-outs that would reflect the needs and requirements of the operator who is buying into the existing network.
A consolidation situation arises when either 2G, 3G or 4G networks, which have already been built out by each of the sharing operators, need to be consolidated into one jointly shared network. This type of network sharing usually holds significant cost advantages, but it also presents substantial design challenges.
Passive Site Sharing
Sharing between two or more Operators including
- Antenna systems, masts, rooftops, cabinets, shelters etc
- Physical space such as compound, security alarms and passive technical facilities such as power supply, battery backup etc.
- Savings of 25-50% on site rental and upto 50% site build and cabinet costs
Sharing between Operators includes
- Antenna systems, masts, rooftops, cabinets, shelters etc
- Antenna and feeder systems technically feasible along with BBU/RRU sharing
- Backhaul sharing in the form of T1, Microwave or DS3 feasible
- Savings are higher than type 1 in the form of NodeB basestations Infrastructure
MORAN (Multi Operator Radio Access Network)
MORAN is the mainstream industry approach to active sharing
- Sharing is device-independent, and does not require any device support to display the correct operator logo
- In the Node B, the radio and power amplifiers remain physically independent in order to allow the operators to use their assigned frequencies.
- The RNC and parts of the Node B are logically partitioned between the sharing parties: logical partition of carriers.
- There are common site-level parameters, but the operators can independently control cell-level parameters: this allows service differentiation. This may be a regulatory prerequisite for network sharing.
MOCN (Multi Operator Core Network)
MOCN is another industry approach for sharing the network.
- specified in 3GPP Release 6
- operators share both the RNC and Node B and pool their frequencies
- spectrum sharing is a major limitation of this solution
- device-dependent, requiring 3GPP Release 6
GWCN (Gateway Core Network)
A Multi-Operator Core Network (MOCN) in which multiple CN nodes are connected to the same RNC and the CN nodes are operated by different operators.
- operators share parts of the core network, in addition to the RAN GMSC, SGSN and VLR
- operators either pool spectrum, or use the spectrum of one of the sharing parties
- GWCN is a historical type of network-sharing solution, which has been superseded by MOCN and MORAN
LTE RAN Sharing
LTE network Configurations are similar to those used for 2G/3G.
- The S1 interface allows it to connect to multiple core networks.
- Spectrum can either be pooled, as in MOCN, or assigned spectrum can be used, as in MORAN.
- A GWCN configuration is also possible where the operators share the MME in addition to the eNodeB.
- the user device informs the eNodeB of the selected core network operator, and the
- eNodeB relays this information to the MME, to ensure the correct operator name is displayed.
- All of these arrangements are supported in the LTE standards (3GPP Release 8 onwards).
What synergy does LTE bring in for RAN sharing? It is the true convergence for 3GPP and 3GPP2 family of networks, as a logical evolution for both families of technologies. It is the first time where technology evolves with both the RAN and CN an all-IP core and OFDM-based modulation for the RF network, ushering in an end-to-end evolution for wireless broadband.
Evolving ecosystems to support Network sharing
SDR (Software Defined Radio)
Software defined radio has several names from the vendors like One RAN solutions or single Radio solutions, and has been around in the R&D phase for probably the longest time. It has been relegated to commercial launch only with the advent of LTE, which specifies among other things SRVCC (Single radio Voice Call Continuity).
Is SDR game changing, in some ways it will be as the design will change on the RF and the baseband. Here is one of older blog-post that delves deeper into SDR.
DNB (distributed NodeB) model brining in cost savings
Distributed base-station into BBU (Baseband Unit) and RRU (Remote Radio Unit), first came into mainstream deployment with the advent of 3G base-stations and has been adopted aggressively by the operators. It helps in reduced Capex, and better uplink performance as cable losses are eliminated, as well as power and HVAC systems savings occur.
Here is one of my older blog-post that talks more about it.
Here LTE networks are technically more suited to active sharing due to their flat all-IP network architecture and operators sharing their active network elements can save at least 40% more in CAPEX and OPEX, over a five-year period, compared to their counterparts striking only passive site-sharing deals. The diagram illustrates an example of end-to-end network architectures for eUTRAN sharing. They differ on how the interconnection is done between the shared eUTRAN and the CN operator networks. Interconnection is done at layer 3 Using a layer 3 connection between the shared eUTRAN and the CN operator networks is really a case by case choice based on the operator.
• IPSEC is used to secure the S1 interface between the eNodeB and each CN operator’s network.
• VLANs are used for traffic separation at the eNodeB.
• IP addressing
• In shared eUTRAN one IP subnet is defined per VLAN per CN operator
• Each eNodeB is configured with the VLAN to be used for each CN operator
• IP is defined at eNodeB for VLAN operator X is taken from the IP subnet defined within the shared eUTRAN for operator X.
• In case of eUTRAN sharing it is important to guarantee a fair access to the shared eUTRAN to the different CN operators.
• Capacity sharing among CN operator is also configured at eNodeB.
Some of the main advantages for RAN sharing include –
- Sharing their infrastructure offers operators massive cost-saving opportunities.
- Infrastructure sharing applies to operators in both developed and emerging markets.
- Operators can implement infrastructure sharing in many different ways.
- In the past, there have been factors that have inhibited infrastructure sharing. These are being removed by regulatory bodies.
- Also LTE brings in convergence in terms of technology divergence from legacy technologies brining in interoperability to both 3GPP & 3GPP2 family.
We can conclude that infrastructure sharing for telecommunications operators is one of the emerging “hot potato” on technologist’s as well as senior management’s agenda. As we have seen the technical approaches that appear viable from today’s perspective, considering currently available technology, and showed how to align these concepts with business and geographic strategies. The economic impact of the various options on operational and capital expenditures of the operators is significant.
RAN sharing models also mean that there will be a loss in revenue to Infrastructure vendors like Ericsson, Nokia Siemens, Alcatel-Lucent, etc. in terms of site-level hardware as well as core hardware. But any such savings could be passed on to the customers in the form of better user experience, capacity augmentation where needed and better SLA’s in terms of performance degradation.