MMDS and LMDS

MMDS allows two-way voice, data and video streaming. It operates at a lower frequency than LMDS (typically within specified bands in the 2-10GHz range) and therefore has a greater range and requires a less powerful signal than LMDS. MMDS is a less complicated, cheaper system to implement. As a consequence, the CPE is cheaper, thus it has a wider potential addressable market. It is also less vulnerable to rain fade - the interference caused by adverse weather conditions that can undermine the quality of the microwave signal. However, the bandwidth offered by LMDS makes this the more viable option.

Advantage of MMDS

• It has chunks of under-utilized spectrum that will, once completely digital, become increasingly valuable and flexible.
• System Implementation, which is little more than putting an installed transmitter on a high tower and a small receiving antenna on the customer’s balcony or roof, is quick and inexpensive.
• Moreover, since MMDS services have been around for 20 years, there is a wealth of experience--at least in respect to the one-way distribution technology.

Disadvantage of MMDS:

• Large upstream bandwidth in MMDS band requires careful planning, filtering etc.
• Limited capacity without sectorization, cellularization which adds complexity and cost

MMDS is a broadcasting and communications service that operates in the ultra−high−frequency

(UHF) portion of the radio spectrum between 2.1 and 2.7 GHz. MMDS is also known as wireless

cable. It was conceived as a substitute for conventional cable television (TV). However, it also has

applications in telephone/fax and data communications.

In MMDS, a medium−power transmitter is located with an omni−directional broadcast antenna at or

near the highest topographical point in the intended coverage area. The workable radius can reach

up to 70 miles in flat terrain (significantly less in hilly or mountainous areas). There is a monthly fee,

similar to that for satellite TV service.

MMDS frequencies provide precise, clear, and wide−ranging signal coverage. Customers are

protected from interference from other users when the provider uses the licensed frequencies. Rain,

snow, and fog do not interfere with signal performance as we saw in the microwave radio chapter

(see Chapter 17, "Microwave− and Radio−Based Systems"). Many of the carriers use a super−cell

concept with a service area spanning a 35−mile radius from each of its MMDS transmitters.

Whenever the concept of the competitive environment enters a discussion, two other discussions

ensue: the WLL and the use of LMDS. This chapter will look at some of the movement in this area

to understand how and why the last mile has become so critical in meeting the demands for

higher−speed broadband communications. Moreover, when looking at the incumbent local

exchange carriers' (ILEC) copper−based plant, one can only marvel at the lack of foresight in

fending off the competition.