Channel Aggregation in 802.16t
Enable High-Throughput Connectivity with Advanced
Spectrum Management Technology
Channel aggregation (also known as spectrum aggregation) is the ability of a wireless network to effectively combine carriers either dispersed continuously or non-continuously within a frequency band(s), but also combine carriers operating with different bandwidths in one or more frequency bands. Spectrum aggregation is a key technology that enables much higher data throughput across legacy narrowband channels such as those operated by the railroads.
In addition to a significant increase in data throughput capabilities, spectrum aggregation also offers stronger resilience to the impacts of fading and better control of channel usage. Spectrum aggregation is also the key to “unlocking” the use of non-continuous channels that previously could not be utilized for rail applications due to technology constraints.
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As noted in the FRA’s Railroad Wireless Communications Roadmap Final Report, one of the key elements to migrate from traditional use of spectrum to more efficient use of spectrum is the ability to refarm and aggregate railroad-owned spectrum. The report notes specific advantages of channel aggregation technology, in particular:
“In contrast to the current scheme, where certain applications are restricted to specific bands, spectrum aggregation and dynamic message assignment would allow applications to dynamically use one or multiple bands simultaneously.”
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Channel aggregation and dynamic spectrum allocation are key features of Ondas Networks' IEEE 802.16t FullMAX radios.
Dynamic Management of Spectrum Resources
The Base Station Controller (BSC) is a central manager of Air Interface Resources (AIRs) utilized by 802.16t base stations and their connected remotes within a general purpose 802.16t radio network. The BSC is the foundation of an 802.16t network and provides bandwidth multiplication and self-interference avoidance which greatly optimizes the utilization of all available spectrum across all users. The BSC is a key building block within the Ondas 802.16t Point-to-Multipoint (PtMP) multicell, multisector system.
The BSC maximizes the use of all channels in a given frequency band by
dynamically allocating spectrum to remote radios whenever it is needed.
Any channels which are temporarily available may be allocated to other
parts of the network to support temporary surges in demand. Thus, 802.16t
allows railroads to maximize the utilization of the spectrum they already
own rather than having to look to procure more spectrum in order to
deploy new applications.
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Non-Continuous Channel Aggregation
Aggregation of Multiple Subchannels
An Ondas Networks base station radio (such as Mars) communicates with fixed and mobile remote radios (such Mercury) on aggregated subchannels. The bandwidth in a sector may consist of a continuous band or an aggregation of multiple adjacent or non-adjacent channels. This channel bandwidth is partitioned into multiple subchannels in the example below. The Ondas base station will operate over the entire channel while Mercury radios operate over single subchannels. Venus remote radios may operate over multiple aggregated subchannels.
Advanced Data Capacity with 802.16t
Through the use of a BSC, an 802.16t network can leverage any available adjacent and non-adjacent spectrum for data. This enables 100% spectrum utilization - a dramatic improvement compared to the very low utilization of frequencies on the narrowband channels.
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As an example of the capacity improvements achievable with 802.16t, we can compare legacy ATCS radio operation and an Ondas Networks FullMAX™ radio operating on the 900 MHz A Block. A legacy ATCS radio operates on a single 12.5 kHz channel pair based on railroad assignment. Since this assignment is fixed, there is no potential reuse of any other available channels even when adjacent channels are unused or inactive. This rendered the legacy ATCS system to be a low throughput, purpose-built network.
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In contrast, an Ondas Networks FullMAX™ radio is capable of aggregating one or all ten channels pairs in the A Block. The channels may be continuous and non-continuous, ensuring that any available spectrum can be used during period of high demand from remote radios. When an Ondas radio aggregates the entire ten channel pairs of the A Block and operates in OFDM / QAM modulation, the end user can achieve a maximum data throughput of 925 kbps – a data capacity improvement of 37x over legacy radio operation!
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Similar results can be achieved on other AAR owned frequency bands as well:
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To learn more about how channel aggregation works in an 802.16t network, and how a BSC enables the highest optimization of spectrum utilization through bandwidth multiplication and self-interference avoidance, click here.