All households need to be connected to the internet these days. Telenor Norway is rolling out fiber access to customers and fiber nodes to shorten the existing cable and copper access lines to offer high-speed internet. Unfortunately, such access modernization is not cost-effective for all rural households. To be loved by customers, Telenor must find a cost-effective and fast access technology for the remaining households. The customers also expect unlimited data quotas at home.
There is a good business case for offering Fixed LTE to households that cannot have fiber, cable or VDSL access to the internet. The case is based on reuse of base stations built for the nationwide mobile LTE network. In addition we need base station antennas and radio equipment for the dedicated Fixed LTE spectrum on sites with line-of-sight to the houses. This is a way to increase the fixed broadband market share in Norway by attracting new broadband customers and upgrading existing Wimax and ADSL customers. Operators that manage to roll out both mobile and fixed LTE simultaneously will reduce the already low marginal cost of Fixed LTE significantly.
A customer pilot in live network has demonstrated that Fixed LTE can offer a VDSL-like user experience. The customers loved the service. In 2-3 years’ time, it is likely that we will experience Fixed LTE at gigabit speeds. This obviously depends on number of households per Fixed LTE cell, available spectrum and terrain properties.
“Fixed LTE” is the name of Telenor Norway’s project referred to in this article. In Telenor Norway, Fixed LTE is seen as a Wireless Broadband Access solution for filling the gap in their fixed access offering by use of standard LTE TDD technology. For other BUs, a similar solution can be worth considering for expanding their products in a way which has significant synergies with their current or planned LTE mobile network.
A wireless solution for households requires dedicated LTE Spectrum
Norway has a very sparse population of 5 million. By the end of 2017, 99.8 % of Norway’s population will have 4G coverage. All mobile base stations will have mobile 4G equipment installed with high-capacity backhaul with either fiber or high-capacity microwave.
Using Mobile LTE as the prime broadband access to the family has several shortcomings. There are often several persons living in each household. Streaming hours of video is surely a popular activity that is not compatible with data quotas that are mandatory in mobile broadband services. Especially in the evenings, 4G traffic generated by the households may create capacity and stability problems when sharing the regular 4G network with mobile users.
This is why Telenor Norway recently acquired 90 MHz (3610-3700 MHz) of Time Division Duplex (TDD) spectrum in the 3.7 GHz band to be used for dedicated Fixed LTE coverage in selected rural areas. This coverage will be completely separated from the mobile LTE network that currently utilizes Frequency Division Duplex (FDD) in the 800, 1800 and 2600 MHz frequency bands. The new spectrum license expires on December 31st, 2022.
The 3.7 GHz band requires careful planning when used over long distances. The Fixed LTE coverage will therefore be very different compared to mobile LTE coverage. This setup works because it is possible to build relatively small and low-cost high-gain antennas for higher frequency bands. The coverage will not support any kind of mobility, so continuous coverage is not necessary. It will be directed towards clusters of houses, thereby optimizing the coverage for outdoor antennas and nothing else.
The Fixed LTE Concept and Product
Each Fixed LTE household must install an outdoor antenna that has line-of-sight to an existing base station with high-capacity backhaul. The outdoor antenna, typically installed on the roof or on a wall outside, is connected via Power-over-Ethernet cable to an indoor router that provides Wi-Fi coverage inside the house and power to the outdoor antenna. The SIM card is inserted in the outdoor antenna so that the CPE may establish an LTE-connection via the mobile core to the internet. The Fixed LTE solution will NOT provide indoor 4G coverage in the households.
In Norway we will use the 3.7 GHz band where we will have enough spectrum for aggregation of four 20 MHz LTE carriers reserved for customers of Fixed LTE. Typical distances between outdoor antennas and the base stations will be 1-12 km.
At each base station with Fixed LTE we will reuse buildings, towers, power, cooling and backhaul established for the mobile 4G network. We will install one, two or three base station antennas and radio equipment to provide dedicated coverage for the Fixed LTE households with line-of-sight.
We will also reuse the existing mobile core network even if we don’t need the mobility functionality. PCRF/Online Charging can be used to implement features such as speed limits for Fixed LTE as a product. Even tunneling of Fixed LTE traffic right through the mobile core has been discussed in order to make Fixed LTE services identical to VDSL services.
The tight integration and sharing of the Fixed and Mobile LTE infrastructures will make Fixed LTE follow the software releases and hardware upgrades of Mobile LTE and mobile core.
The Fixed LTE concept is intended as a fixed access broadband product with fixed cost per month depending on maximum speed. There will be no data volume quota. In principle, the user experience in each household will be similar to a VDSL service. It is not yet decided whether the service will be exactly the same as VDSL (including security services, walled garden, etc.) or just plain internet access. It will work perfectly with Voice over Wi-Fi.
Proof of Concept based on Pilot with Customers in Live Network
In close cooperation with Huawei, Telenor Norway conducted an external Fixed LTE pilot in live network in two village areas. The pilot utilized two 20 MHz LTE carriers in the 3.7 GHz band.
The Fixed LTE pilot was conducted as a proof of concept. Focus was on customer experience in real-life scenarios and efficient operations over time. Customers received the necessary equipment and subscriptions with no data volume limit. Huawei provided the equipment.
At Skollenborg Fixed LTE was installed at 2 base station sites and at 19 households at 4-10 km from the base stations. Most of them were existing Wimax customers. We had no major problems during the pilot that lasted for 9 months. This is partly due to reuse of Wimax line-of-sight planning. We used both one carrier and two carrier configurations during the pilot. Since the CPEs did not support carrier aggregation, we used load balancing in two-carrier configurations instead so that the base station (eNodeB) could assign households to different carriers.
At Nesodden we had 17 households connected for 3 months at 5-10 km from the base stations. The figures below show the partly overlapping coverage from Fixed LTE base stations at Vettre and Telenor Fornebu. In this second pilot area we wanted to test more challenging line-of-sight scenarios and to verify that long stretches of water (~10 km) do not create any problems. Twelve of these households belonged to Telenor employees. We also got the chance to do the radio planning from A to Z.
In both Skollenborg and Nesodden we established overlapping coverage on purpose from two Fixed LTE base stations for almost all houses at Skollenborg and for a third of the houses at Nesodden. We concluded that interference was no major problem under typical traffic loads.
Three of the households at Nesodden had consistent poor service from the base station at Vettre. The most probable cause seems to be trees close to the base station mast at Vettre blocking line of sight in the direction of these three houses at Nesodden. This underscores that line-of-sight issues require serious attention during planning. Since the radio planning and line-of-sight verification is such an important activity before rollout of Fixed LTE for households in an area, we strongly recommend a project-based rollout.
Results from the Fixed LTE Pilot
The initial phase of the pilot in Skollenborg demonstrated that approximately 20 households in one sector with one 20 MHz carrier on one site can provide on average 30 Mbit/s downlink and 5 Mbit/s uplink for each household under normal household use. It is important to remember that all users in each household (family) must share the 30/5 capacity. During the pilot we experienced spiky traffic even for Full HD video streaming. That leaves ample opportunity for overbooking of capacity. Most of the time we used two carriers, but since the first generation of CPEs does not support carrier aggregation, we tested multi-carrier workload balancing instead.
Telenor Norway expects that a commercial deployment of Fixed LTE can provide an average speed per household of at least 100 Mbit/s downlink and 10 Mbit/s uplink within the next 1-2 years. That is according to Huawei’s roadmap for base station equipment and CPEs that can aggregate the four carriers that Telenor Norway has acquired and utilize features like 4x4/8x8 MIMO and 64/256 QAM modulation. Maximum downlink speed will eventually reach 1 Gbit/s.
During the pilot we used existing mobile operations support systems (OSS). Instead of business support system (BSS) we established manual processes to handle customer issues and faults. To minimize CAPEX and OPEX in a commercial launch, it is necessary to decide on the business model for Fixed LTE as early as possible. This model will decide which IT solutions that are needed and how processes for planning, rollout, sales, delivery, customer service, fault handling and billing are affected. Remote management of the Fixed LTE CPEs based on TR-069 (CPE remote management protocol) will be essential for scalability. If an intermediate BSS solution is established, it is important to ensure that it can scale with the customer demand until a permanent BSS solution can be developed.
We received very positive feedback from the customers both during and after the pilot. Several customers used more than 100 GB a month. The maximum was around 200 GB. With separate frequency bands we avoided that Fixed LTE customers took capacity from the mobile customers, and vice versa.
The overall conclusion is that Fixed LTE works well in practice. Almost all pilot customers would have liked to continue using the Fixed LTE service as a payable service, even in the rudimentary pilot setup. The only exceptions were customers that were offered fiber access (from one of Telenor’s competitors) and 2-3 customers that experienced line-of-sight issues during the pilot. Two pilot customers at Skollenborg even wanted Fixed LTE rather than fiber access!
We have confirmed that Fixed LTE can piggyback on the Mobile LTE infrastructure that Telenor is currently rolling out nationwide. The low marginal cost of adding Fixed LTE antennas and radio units on site makes the business case very promising. Simultaneous rollout of Mobile and Fixed LTE would reduce the marginal subcontractor cost tremendously, especially with Norway’s bid regime for subcontractors. The pilot at Skollenborg has confirmed beyond doubt that Fixed LTE can replace the Wimax product and instances of ADSL infrastructure.
Project-based rollout is essential to ensure line-of-sight from each base station to the houses it covers, and to ensure sufficient capacity for all the households. Near line-of-sight may be OK, but small changes in the terrain may on short notice turn into non-line-of-sight that can ruin the Fixed LTE service for the affected households. We learnt that even Full HD video traffic is not very demanding on the Fixed LTE capacity because of its spiky nature caused by buffering. Interference with overlapping coverage did not seem to be a problem, but it is easy to imagine heavy traffic scenarios that may cause interference issues.
Last, but not least, Fixed LTE seemed to be a very engaging service that was loved by its customers.
About this Article
The author of this article is Vidar Vetland, CTO office and architecture in Telenor Norway. Please contact Vidar for more detailed information, further questions or comments.