Efficient Voice over Internet Protocol (VoIP) on Mesh Networks
 Mobile Military communicationsTested VOIP Communications with SIP phonesMeshDynamics VOIP test in underground mine 


Besides the inherently high performance of Meshdynamics' patented multi-radio backhaul technology, additional specialized voice features minimize delay and jitter. These features insure that voice is transported rapidly and efficiently across the network, maximizing the number of voice calls that may be supported while minimizing wasted bandwidth.

Extensions for Low latency, near isochronous M2M messaging is discussed. This is relevant to the Application Layer , where Enterprise applications reside, on the mesh node.

Latency/Jitter Degradation on Single Channel Backhauls

Latency is inversely related to available bandwidth: thin pipes can provide only so much flow. Single channel backhauls suffering from bandwidth degradation also suffer from poor latency and jitter over multiple hops. This is primarily due to the need for a single radio to serve both backhaul and client traffic. The result is that most First Generation single-channel backhaul networks provide reliable video- or voice service over only one- or two hops. As a result many more costly wired or fiber Internet or intranet drops are needed to deliver adequate service, increasing the ongoing total cost of ownership.
Third Generation mesh products do not suffer from bandwidth degradation – they use multiple backhaul radios to obviate radio channel interference. Field tests indicate a latency of less than 1 millisecond per hop even under heavy traffic. Since latency is thus not a factor of traffic or user density, jitter (variation in delay) is also very low. This makes Third Generation products suitable for networks serving large number of users, demanding applications, video, and voice -- even simultaneously.

Additionally, Meshdynamics multi-radio backhauls also incorporate VOIP concatenation for timely VOIP packet delivery. VOIP packets are small – typically less than 300 bytes but sent frequently, generally once every 20 milliseconds. Networking protocols like CSMA/CA don’t transport small and time sensitive packets well. The VOIP concatenation engine aggregates small VOIP packets into a larger packet for more efficient delivery. This aggregation takes place every 5-10 milliseconds. USAF tests show overall latency is less than 10 ms + 1 ms per hop over a 4 hop network. Jitter is less than 1 ms. per hop.

 Meshdynamics multi-radio multi-channel backhaul ensures deterministic latency and jitter by eliminating both the effects of single radio backhauls and involuntary contention. 

Figure 1a (left): Latency for 36 simultaneous VOIP calls over a 4 hop Mesh running VOIP Concatenation over the backhaul.
Figure 1b (right): Jitter for 36 simultaneous VOIP calls over a 4 hop Mesh running VOIP Concatenation over the backhaul.

Figure 1 Explanation:
Since VOIP packets are small, inefficiencies related to transmitting small packets result in significant overhead. This adversely affects usable capacity. The Meshdynamics concatenation engine puts VOIP packets into a "container" packet. Containers are shipped periodically much like a bus arrives and leaves as a bus station at regular intervals. Bulk transport of VOIP packets is thus more efficient. Latency/jitter is also better managed than if the VOIP packets were individually transmitted - where they would be contending with each other. Our multi-radio multi-channel backhaul ensures deterministic latency and jitter by eliminating both the effects of single radio backhauls and involuntary contention.  Patent

Persistent Base VoiceTM (PBV)

With the Application Layer in place, applications like our Persistent Base VoiceTM (PBV) have been built. With PBV, VOIP phones can function even when the SIP gateway is not reachable: the mesh nodes act as a temporary proxy SIP server till nodes rejoin the main mesh.  Beyond sharing SIP registries between previously isolated network clusters, applications like PBV need  accurate estimates of how long a VOIP packet will take, with -- and without -- concatenation overheads. If  the bus shuttle schedule is appropriately timed, to miss a majority of packets that arrive, then bus schedules are dynamically revised.

Please also see  Press Release    Illustration     Patent

Application Extensions For Industrial Internet of Things (IIOT)

With deterministic jitter and latency in place, accurate estimates are computed on the "round trip" delay from wireless end devices to cloud and back. This information, computed periodically, is available to applications resident on the mesh nodes.. They may choose to use the VOIP concatenation for their own M2M feeds as part of a their internal publish subscribe M2M ecosystem.

Machine to Machine communications, like VOIP, are typically terse and preferably isochronous. Applications, like PBV, access current jitter and latency from source to destination, for different clients on the mesh network -- each with their own sender-receiver transmission routes -- and then determine the best bus shuttle service and schedule for VOIP concatenation based routing.

Related to VOIP Concatenation Engine

1. Meshdynamics receives Prestigious VIEW certification Certification received from Spectralink/Polycom
2. Meshdynamics First With Persistent Voice Over Wireless Mesh VOIP calls work even when no SIP server is present. 
3.   Meshdynamics Delivers Persistent Wi-Fi Network for Mobile Environments  Merging and dispersal in mobile networks
4. Wi-Fi based Femtocell Extensions for the outdoor enterprise. Extension of Femtocell coverage using mesh.
5. VOIP and VIDEO on a City wide scale Meshdynamics VOIP Concatenation Engine explained..