Motorola PTP Overiew

Motorola’s PTP 400 and PTP 600 Series wireless Ethernet Bridges can deliver up to 99.999% availability in even the most challenging environments. Plus, they’re cost-effective, faster to deploy and easier to manage than comparable systems. They offer more capacity and higher signal quality over greater range – even over water. And they provide greater spectral efficiency, which allows high performance in areas with congested radio communications. Operating at Ethernet data rates up to 300 Mbps, the systems support a wide variety of demanding applications, including:

• Linking networks in a campus setting
• Voice-over-IP and video surveillance
• Transmitting across long distances, over water or around obstacles
• Handling last-mile and heavy-duty backhaul traffic
• Migrating from an analog to a digital network
• Linking separate loops within individual buildings
• T1/E1 replacement

Motorola 400/600 Comparison

Multiple-Input Multiple-Output (MIMO)
Non-line-of-sight (NLoS) environments create all kinds of signal issues. Connections are subject to massive periodic fading, often dropping to 1/10,000th of the already highly attenuated level. Signals are prone to be out-of-phase, because there is no main path, just many indirect paths of similar energy, dramatically raising the risk that signals will cancel each other. With Motorola’s MIMO technology, numerous data streams are transmitted between multiple transmitters and receivers. At the receiving end, all the data streams are compared and evaluated until the data image is accurately restored and sequenced. The result is significantly reduced NLoS fading, providing consistently reliable, high-quality
communications in even the toughest environments.

Intelligent Orthogonal Frequency Division Multiplexing (i-OFDM)
In NLoS environments, signals arrive by many different (dispersed) paths. The path lengths vary, so the signals also arrive at different times. In addition, the paths have different delay characteristics, causing previously transmitted data bits to interfere with current data bits. This interference is known as multipath inter-symbol-interference or ISI. Conventional radios resolve the problem using an ISI equalizer. Many NLoS vendors employ some form of OFDM (Orthogonal Frequency Division Multiplexing) to overcome this problem, but none of them add the intelligence that is embedded in Motorola’s intelligent OFDM.

Advanced Spectrum Management with i-DFS (Intelligent Dynamic Frequency Selection)
Channel frequencies can be set either manually or dynamically. The Motorola PTP 400 and 600 families of wireless bridges monitor all available radio channels – 500 times a second – and dynamically select the frequency over which they can sustain the highest data rate at the best quality. This means that the bridges are very likely to find a clear channel
(without operator intervention) even in a crowded space. Our 30-day, time-stamped database alerts the operator to any interference that does exist and provides statistics that help pinpoint the channels that provide the clearest data paths. From the user’s point of view, this experience is equivalent to having exclusive rights to use a licensed channel.

Adaptive Modulation
Adaptive Modulation continually optimizes signals according to the conditions of the radio frequency (RF) path, allowing transmissions to travel from one receiver to the next without signal loss. The radio power output is dynamically modified according to the received signal level, upshifting or downshifting to overcome fading. Since the channel may vary in intensity on a sub-second basis, adapting the modulation dynamically allows the maximum amount of data possible to be sent across the path while keeping the link quality at the highest level. Available modulation modes include 256 QAM, 64 QAM, 16 QAM, QPSK, BPSK, multiple FEC rates, single and dual payload.

Time Division Duplexing (TDD) Synchronization
Multiple radios that are located in close proximity to each other – typically on the same tower or rooftop – can generate significant amounts of interference as the radios send and receive data. As an example, if radio-1 is transmitting when radio-2 is receiving, radio-2’s incoming transmission can be interfered with even if the transmissions are on different
frequency channels. Because radio-1’s signal is so close, it is strong enough to “flood” or interfere with the communications flowing to radio-2. To eliminate such interference, it is important that all the radios on the tower or rooftop transmit at the same time and receive at the same time. On PTP 600 Series bridges, Motorola’s TDD Synchronization capability times and synchronizes transmit and receive signals, enabling efficient frequency reuse. This allows network operators to co-locate multiple radios on a rooftop or tower without
the radios interfering with each other. The TDD Synchronization is accomplished using an external GPS Synchronization Unit that ties all radios in the designated network to the same “clock.”

Spatial Diversity
The PTP 400 and PTP 600 families of point-to-point radios have inherent spatial diversity capability to combat ducting and multipath fading, allowing communications to travel over water, across vast expanses of open terrain and in deep non-line-ofsight environments without signal loss. As radio waves travel across distances, especially over water and flat terrain, they run an increased risk of multipath interference caused by signals reflecting off the water, desert or flat plain. This interference can cause the signals to cancel each other as they travel to the receiver from various directions over multiple paths. In addition, signals can experience ducting as they move through air masses of different densities, which deflect the signals away from the receiving antenna, often cutting communication between radios.