Backhaul, which is the connection between a radio node and the core network, is providing mobile-wireless operators possible with the biggest headache ever (apart from keeping a healthy revenue growth in mature markets 😉 … it can be difficult to come by in the right quantities and can be rather costly with conventional transmission cost-structures … Backhaul is expected to have delayed the Sprint WiMAX rollout of their Xohm branded wireless internet service. A Sprint representative is supposed to have said: “You need a lot of backhaul capacity to do what’s required for WiMax.” (see forexample WiMax.com blog)
What’s a lot?
Well … looking at the expected WiMAX speed per Base Station (BS) of up-to 50 Mbps (i.e., 12 – 24x typical backhaul supporting voice demand), it is clear that finding suitable and low-cost bachaul solutions might be challenging. Conventional leased lines would be grossly un-economical at least if priced conventionally; xDSL and Fiber-to-the-Premises (FTTP) infrastructure that could support (economically?) such bandwidth demand is not widely deployed yet.
Is this a Sprint issue only? Nope! …. Sprint cannot be the only mobile-wireless operator with this problem – for UMTS/HSPA mobile operators the story should be pretty much the same (unless an operator has a good and modern microwave backhaul network supporting the BS speed).
Backhaul Pains – Scalability Issues
The backhaul connection can be either via a Leased Line (LL) or a Microwave (MW) radio link. Sometimes a MW link can be leased as well and might even be called a leased line.
With microwave (MW) links one can easily deliver multiples of 2.048 Mbps (i.e., 10 – 100 Mbps) on the same connection for relative low capital cost (€500 – €1,000 per 2.048 Mbps) and low operational expense. However planning and deployment experience and spectrum is required.
In many markets network operators have been using conventional (fixed) leased lines, leased from incumbent fixed-line providers. The pricing model is typically based on an upfront installation fee (might be capitalized) and a re-occurring monthly lease. On a yearly basis this operational expense can be in the order of €5,000 per 2.048 Mbps, i.e., 5x to 10 x the amount of a MW connection. Some price-models trade-off the 1-off installation fee with a lower lease cost.
Voice was the Good for Backhaul; Before looking at the broadband wireless data bandwidth demand its worth noticing that in the good old Voice days (i.e., GSM, IS95, ..) 1x to 2x 2.048 Mbps was more than sufficient to support most demands on a radio base station (BS).
Mobile-Wireless Broadband data enablers are the Bad and quickly becoming the Very Ugly for Backhaul; With the deployment of High Speed Packet Access (HSPA) on-top of UMTS and with WiMAX (a la Sprint) a BS can easily provide between 7.2 to 14.4 Mbps or higher per sector depending on available bandwidth. With 3 sectors per BS the total supplied data capacity could (in theory … ) be in excess of 21 Mbps per radio Base Station.
From the perspective of backhaul connectivity one would need at least an equivalent bandwidth of 10x 2.048 Mbps connections. Assuming such backhaul lease bandwidth is available in the first instance, with conventional leased line pricing structure, such capacity would be very expensive, i.e., €50,000 per backhaul connection per year. Thus, for 1,000 radio nodes an operator would pay on an annual basis 50 million Euro (Opex directly hitting the EBITDA). This operational expense could be 8 times more than a voice-based operational leased-line expense.
Now that’s alot!
Looking a little ahead (i.e., next couple of years) our UMTS and WiMAX based mobile networks will undergo the so-called Long-Term Evolution (LTE; FDD and TDD based) with expected radio node downlink (i.e., base station to user equipment) capacity between 173 Mbps and 326 Mbps depending on antenna system and available bandwidth (i.e., minimum 20 Mhz spectrum per sector). Thus over a 3-sectored BS (theoretical) speeds in excess of 520 Mbps might be dreamed of (i.e., 253x 2.048 Mbps – and this is HUGE!:-). Alas across a practical real-life deployed base station (on average) no more than 1/3 of the theoretical speed should be expected.
“Houston we have a problem” … should be ringing in any CFO / CTO’s ears – a. Financially near-future developments could significantly strain the Technology Opex budgets and b.Technically providing cost-efficient backhaul capacity that can sustain the promised land.
A lot of that above possible cost can and should be avoided; looking at possible remedies we have several options;
1. High capacity microwave backhaul can prevent the severe increase in leased line cost; provided spectrum and expertise is available. Financially microwave deployment has the advantage of being mainly capital-investment driven with resulting little additional operational expense per connection. It is expected that microwave solutions will be available in the next couple of years which can provide connection capacity of 100 Mbps and above.
Microwave backhaul solutions are clearly economical. However, it is doubtful that LTE speed requirements can be met even with most efficient microwave backhaul solutions?
2. Move to different leased line (LL) pricing mechanisms such as flat pricing (eat all you can for x-Euro). Changing the LL pricing structure is not sufficient. At the same time providers of leased-line infrastructure will be “forced” (i.e., by economics and bandwidth demand) to move to new types of leased bandwidth solutions and architectures in order to sustain the radio network capabilities; ADSL is expected to develop from 8(DL)/1(UL) Mbps to 25(DL)/3.5(UL) Mbps with ADSL2+; VDSL (UL/DL symmetric) from ca. 100 Mbps to 250 Mbps with VDSL2 (ITU-T G.993.2 standard).
Clearly a VDSL2-based infrastructure could support today’s HSPA/WiMAX requirements, as well as the initial bandwidth requirements of LTE. Although VDSL2-based networks are being deployed around Europe (and the world) it is not not widely available.
Another promising mean of supporting the radio-access bandwidth requirements is Fiber to the Premises (FTTP), such as for example offered by Verizon in certain areas of USA (Verizon FiOS Service). With Gigabit Passive Optical Network (GPON, ITU-T G.984 standard) maximum speeds of 2,400 Mbps (DL) and 1,200 Mbps (UL) can be expected. If available FTTP to the base station would be ideal – provided that the connection is priced no higher than a standard 2.048 Mbps leased line to day (i.e., €5,000 benchmark). Note that for a mobile operator it could be acceptable to pay a large 1-off installation fee which could partly finance the FTTP connection to the base station.
Cost & Pricing Expectations
It is in general accepted by industry analysts that broadband wireless services are not going to add much to mobile operators total service revenue growth. In optimistic revenue scenarios data revenue compensates for stagnating/falling voice revenues. EBITDA margins will (actually are!) under pressure and the operational expenses will be violently scrutinized.
Thus, mobile operators deploying UMTS/HSPA, WiMAX and eventually (in the short-term) LTE cannot afford to have its absolute Opex increase. Therefore, if a mobile-wireless operator has a certain backhaul Opex, it would try to keep it at the existing level or reduce it over time (to mitigate possible revenue decline).
For the backhaul leased-capacity providers this is sort of bad news (or good? as it forces them to become economically more efficient) …. as they would have to finance their new fixed higher-bandwidth infrastructures (i.e., VDSL or FTTP) with little additional revenue from the mobile-wireless operators.
Economically it is not clear whether mobile-wireless cost-structure expectations will meet the leased-capacity providers total-cost of deploying networks supporting the mobile-wireless bandwidth demand.
However, for the provider of leased fixed-bandwith, providing VDSL2 and/or FTTP to the residential market should finance their deployment model.
With more than 90% of all data traffic being consumed in-house/in-door and with VDSL2/Fiber-to-the-Home (FTTH) solutions being readily available to the Homes (in urban environments at least) of business as well as residential customers, will mobile-wireless LTE base stations be loaded to the extend that very-high capacity (i.e., beyond 50 Mbps) backhaul connections would be needed?