Microwave transmission systems are straining under increased bandwidth needs. Modern microwave systems use advanced packet compression and higher-order modulation to increase channel capacity, but at some point there’s the need for increasing the number of radio channels used to boost capacity.
Multichannel systems offer a number of benefits. They create a virtual link from two or more underlying channels and the resultant capacity is the sum of the number of channels used. Individual channels in the multichannel bundle can have different profiles for frequency bands, modulation levels and capacities. Adaptive modulation can be enabled across all channels in the multichannel bundle. Legacy and new IP traffic can use a multichannel virtual link as a whole, and the rigid association between the capacity a service requires and the capacity a radio channel offers is removed. Also, microwave link protection can move from a traditional N+1 spare channel approach to a more effective multichannel N+0 approach.
Standard radio link aggregation (LAG) suffers from a rigid association between a flow and a specific channel in a virtual link, and every channel in a virtual link must support the same capacity. This is seldom possible with microwave networks because of the effects of adaptive modulation on individual channels.
Multichannel Radio LAG overcomes these challenges by distributing traffic load evenly based on algorithms that do not leave channels underutilized or impact services, however, and it does not require each channel in a bundle to have the same capacity as the most demanding service.
“Unlike traditional N+1 techniques to scale microwave link capacity, multichannel systems do not require spare protection channels to protect link capacity,” noted a recent TechZine article, “Multichannel Radio LAG Improves/Scales Microwave,” by Paolo Volpato, Product Strategy Manager, Wireless Transmission, Alcatel-Lucent (News - Alert) on the topic. “Instead, multichannel systems use the concept of spare capacity across a bundle of active channels.”
‘He added: “From a network design standpoint, the probability of delivering the committed traffic is very high. That’s because the degradation on one channel can be compensated for with the excess capacity available on other channels in the bundle.”
Multichannel Radio LAG is a more flexible, efficient and reliable approach to scaling microwave capacity over traditional N+1 LAG systems.
By using Multichannel Radio LAG, network operators can focus on the actual capacity required instead of needing to emphasize the availability of frequency bands and channel spacing.
“This gives link designers more flexibility,” noted Volpato. He concluded by stating that, “Most importantly, it helps network operators make better use of scarce radio spectrum and decrease network operational expenses.”
Edited by Peter Bernstein