• MMDS Systems

• Overview and Key Features
• System Description
• Product Guide
• Data Sheets
• Customer Installs Digital Systems
• Customer Installs Analog Systems
• Contacts for Quote

Cable AML offers 2 types of MMDS systems:

• Analog MMDS Systems
• Digital MMDS Systems

Analog MMDS System Description

The key elements of an analog MMDS system are:

• Headend
• Transmitter & Antenna
• Subscriber Equipment

 

The Headend

The Headend is the point of origin for the TV signals that are transmitted through the system. A typical Headend will include:

• Equipment such as signal processors, demodulators and Satellite Receivers to generate input baseband video and audio signals.
• Modulators, which accept baseband video and audio signals and deliver standard modulated carriers in the 222 to 406 MHz frequency range. The combined output of the modulators is then fed to the broadband transmitter.
• An optional Encoding System to scramble some channels or an addressable control system to control the decoders at the subscriber’s premises.

The Transmitter

The Transmitter converts the broadband signal provided by the modulators to the transmit microwave frequency (2500 to 2586 MHz) and amplifies the resulting microwave signal to the power level desired for transmission.

If the transmitter is a distance away from the Headend, Cable AML's broadband microwave links can provide transport of the video signals from the Headend to the MMDS transmitter.

Cable AML’s MMDS broadband transmitters feature linearization circuits for maximum power with minimum distortion. Cable AML MMDS transmitters can be field upgraded for greater output power or to provide for redundant transmitter operation.

The Transmitting Antenna

The Transmitting Antenna system includes the cables or waveguide connecting the transmitter to the antenna, as well as the antenna itself and, if required, the pressurization system for the antenna. The radiation pattern of the transmitter antenna (polarization, azimuth coverage, electrical tilt and gain) have to be selected to match the desired geographical coverage for a given transmitter height and location.

The Subscriber Equipment

The Subscriber Equipment consists of an outdoor unit (an integrated antenna + down-converter), which converts the received microwave signal to frequencies in the 220 to 408 MHz range, which is suitable for feeding standard TV sets. The outdoor unit is connected through a coaxial cable to the subscriber’s home wiring or directly to the TV set.

If the signals are transmitted “in the clear” (without encoding) the output of the outdoor unit can be connected directly the subscriber’s TV set. If the signals are encoded, an indoor STB (set-top box) is used with the subscriber's television receiver.

Several types of outdoor units are available, depending on requirements for antenna gain, size, and availability of features such as interference reduction filters, etc. The set-top decoder is determined by the choice of encoding system.

Encoding System Options

A fundamental decision in an MMDS system is to determine the type of encoding system that will be used.  Although many systems can start broadcasting in the clear, channel encoding (at least for some channels) must be addressed from the very beginning.

Signal security is obviously the key concern prompting operators to incur the additional expense of an encoding system, but not the only one.  The type of encoding system will determine the system’s ability to offer different Programming Tiers. Addressability features will determine the system’s ability to offer Pay-Per-View (PPV) capability.

Several options are available for example:

Addressable Down-converters

The addressable converters make it possible to connect or to disconnect service to each subscriber by means of instructions sent through a PC in the Headend. 

The addressable subscriber equipment includes an addressable down-converter with an antenna, A/C power supply and power inserter.

Encoding System without Set-Tops

This system makes it possible to encode any number of channels.  The channels are encoded as a block and the decoders decode all the channels as a block.

In the subscriber's building there is only one decoder connected immediately following the down-converter. This decoder decodes all the channels as a block, so that the TV sets in the subscriber’s home do not need set-top boxes. 

There are two types of subscriber's decoders: 

• Decoders for basic service only. These decoders allow the subscriber to see either all the channels or none of the channels.
• Decoders for basic and premium: these decoders allow the subscriber to see a basic package of channels or the basic plus a premium package of up to four channels. 

Encoding System with Set-Top Boxes

This equipment is the most versatile and can encode any number of channels.  A set-top box is required in each of the subscriber’s TV sets to decode the channels.  The channels can be decoded one by one (not necessarily as a block, like in the previous case).

Digital MMDS System Description

Cable AML’s digital MMDS system in the 2,500 to 2,686 MHz band can be configured to broadcast up to a total of 186 TV programs.  Each 6 MHz wide frequency slot can carry from one to 6 TV NTSC or PAL programs.  The system can also be easily upgraded (in the field) to provide high-speed two-way Internet Access service to a large number of subscribers (several thousand).

A one-way digital MMDS system consists of the following key elements:

 

Headend

The Headend includes modules which accept analog baseband video and audio inputs, convert them to digital data, multiplex the data streams into a single carrier and modulate the carrier with 64-QAM modulation. The other elements of the Headend are the CAS (Conditional Access Systems), the EPG (Electronic Program Guide) and the Subscriber Management System. The CAS controls which subscribers are authorized to decode programs and which programs each subscriber is authorized to watch.

Transmitter System

The Transmitter System includes the broadband transmitter or transmitters and the transmission equipment (antennas and accessories).  The transmitters are usually located near the antennas to minimize signal loss through the transmission lines connecting the two.

The Transmitting Antenna

The Antenna System includes the cables and waveguide connecting the transmitter to the antenna, as well as the antenna itself and, if required, the pressurization system for the antenna.  The radiation pattern of the transmitter antenna (polarization, azimuth coverage, electrical tilt and gain) have to be selected to match the desired geographical coverage for a given transmitter height and location. 

Subscriber Equipment

Subscriber Equipment consists of an outdoor unit (an integrated antenna down-converter) suitable for 64-QAM digital signals.  The outdoor unit is connected through a coaxial cable to the subscriber’s home wiring or directly to the STB (Set Top Box), which in turn feeds the subscriber’s TV set. Several types of outdoor units are available, depending on required antenna gain, size, and features such as interference-reduction filters, etc.  The type of set-top decoder used is determined by the CAS (Conditional Access System).

CAS (Conditional Access System)

The key reasons prompting operators to incur the additional expense of a CAS system are:

• Ability to remotely disconnect the signal to non-paying subscribers.
• Signal security to impede unauthorized use of the MMDS signals.
• Availability of different programming tiers (for example basic, premium, etc).
• Pay-Per-View (PPV) capability.

A CAS system can provide some or all of the above capabilities. Cable AML offers the CAS system, which has been specifically optimized to provide digital MMDS systems with a high level of functionality and high security at a reasonable cost.

We currently offer two varieties of CAS:

• The CAS-A provides on/off control of STBs.
• The CAS-B, in addition to overall signal on/off control, provides program-by program on-off control at each subscriber. As many as 64 tiers can be enabled or disabled in each STB. A tier may be one video program or several video programs, for example a it could be a Basic Tier or a Premium tier. This feature also permits implementation of a Pay per View system.

The CAS runs in a CAMC (Conditional Access and Management Console) PC workstation. The console has a Command Line Interface to control up to 24,000 Set Top Boxes, and in the case of CAS-B, 64 tiers in each box. The CAMC retains the list of authorized STBs and their subscription information.