MMDS and LMDS

Chapter 18: MMDS and LMDS

Multichannel Multipoint Distribution System (MMDS)

             MMDS has been around since 1970s. This is another technology for wireless broadcasting to internet access. TV transmission has been using MMDS for more than 30 years. MMDS is using terrestrial-based radio transmission located at a highest location in a metropolitan to deliver its service. Every MMDS subscriber has a small, exclusive, digital receiver placed at the location that is at the line of sight to the transmitters.  MMDS  operates at higher portion of  the spectrum called the ultra high frequency which ranges from 2.1-2.7 Ghz. MMDS has been known as the substitute for cable television though there are some applications like Telephone/fax and data transmission that MMDS also has. MMDS is using omni-directional antenna located at the higher topographic that is intended to cover the area below which MMDS can transmit data. MMDS can run to license and unlicensed channel which can come in 6MHz chunks and has a transfer rate that would reach 27Mbps or up to 1Gbps when over licensed channels. It has a workable radius that is 70 miles in a flat terrain and significantly less in mountainous or in a hilly areas.

MMDS simple Topology:

               MMDS is known for its precise, clearer and wide-ranging signal coverage which is ideal to have in any provider. There are some instances that weather interferes with the provider; MMDS can protect users to that. Many of the carriers use a super-cell concept with a service area spanning a 35 mile radius from each of its MMDS transmitters. There are 33 analog video channels with 6MHz wide that MMDS originally consist of but now as the technology evolves video channels can now turn into digital and would convert these to 99 channels. The combination of super cells and sectors enable the carrier to reuse the same frequency many times by building multiple cell sites.

When enough customers sign on and as their bandwidth demands grow, the growth in traffic can be handled expeditiously through a new cell or a new sector

Architecture for MMDS

LMDS

LMDS (Local Multipoint Distribution Service) is a broadband wireless point-to-multipoint specification utilizing microwave communications.

LMDS operates on FCC licensed frequencies. The FCC divided the United States into 493 BTA's (Basic Trading Areas) and auctioned the rights to transmit on the LMDS bands in each of those areas to LMDS service providers. Each BTA is licensed to two LMDS service providers. 

What is LMDS?

The term LMDS stands for Local Multipoint Distribution Service. LMDS uses microwave signals to transmit voice, video, and data signals using low power which can reach distances no greater than a five mile range. It is a wireless broadband service that relies on microwave radios to send large amounts of information between each of the radios at very high speeds. It operates between the 28Ghz & 29Ghz bands (Specifically): 27.50Ghz - 28.35Ghz & 29.10Ghz - 29.25Ghz & 30.00Ghz & 31.075Ghz - 31.225Ghz. 

How does LMDS work?

Microwave radios designed to be used with LMDS are installed at two separate sites which are within a five mile range of each other. One of the radios is installed at the LMDS Hub or station and the other is installed at the customers site. The two radios can then transmit very large amounts of information between the two locations. The Hub or station is located at a key position to interface directly with land line fiber optic backbones as well as standard telephony. Video conferencing, Voice, Data, Internet access, and TV signals can all be provided even at the same time through this wireless service.

Why would I want to use LMDS?

One situation might occur when a large company has buildings which are spread out over a campus. However, a portion of the campus is divided by a freeway. In this example it is not cost effective to be able have land lines installed under the freeway to allow communication to the other half of the campus. LMDS radios can be installed on either side of the freeway to enable communications which were previously not feasible. In addition, the radios can be installed on each building throughout the campus to have direct communication internally rather than using the local phone company.

Another situation that may occur is a new high rise that is in need of fiber optic service. However, the building is far from the localfiber ring and it would take a large amount of money and over a year to have it installed. LMDS radios can be installed in as little as a weeks time and can provide fiber optic like services.

Viginia Tech purchased LMDS licenses and partnered with an equipment provider and has systems running.