A DCME Opportunity
Operators across developing countries have been astounded by the huge and rapid success of HSPA. Whether you have a Media Gateway or not, a DCME voice compression solution provides an advanced compression rate and offers an efficient evolution path to an all-IP network to support the rapidly growing demands HSPA places on network infrastructure.
A common challenge
Network departments are often forced to rapidly react to new 3G/HSPA service initiatives in order to avoid horrible bandwidth capacity bottlenecks. With typically less than a month lead time, Network departments are confronted with revamping networks using limited personnel, equipment and financial resources.
Quick and simple assessment
While at first glance it may seem a short-term tactical implementation, revamping voice traffic management and compression is a quick and simple improvement that offers immediate and long–term benefits. DCME compression is a sophisticated method of freeing-up high-quality bandwidth on the existing network to accommodate premium 3G traffic, avoiding customer churn and improving revenue potential.
A Plug and Play Solution
Memotec’s DCME solution offers a 16:1 compression rate with sustained quality. It’s a plug and play implementation that relieves bottleneck pain points instantly and seamlessly integrates within the existing IP network.
DCME Solutions for Telephony Applications
DCME systems that provide digital PCM voice compression have been in use in telephony networks for many years, in particular for use over expensive or limited bandwidth transmission media such as satellite links and PDH (microwave) terrestrial lines.
As voice revenues decline for incumbent telephony operators, reducing network-operating costs (OPEX) becomes a key issue to maintain profitability. The superior performance of Memotec's DCME can help telephony operators reduce their transmission operating costs.
International Satellite Links
International Satellite Links is one of the most obvious applications where Memotec's advanced DCME solutions can offer telephony operators significant OPEX savings.
SS7 Traffic Backhaul
In a telephony network, the SS7 traffic is often carried out-of-band over a dedicated transmission network distinct from the transmission network used for carrying voice traffic for reliability purposes. Given the very high availability level of satellite transmission (better than 99,9%), satellite links are often used for carrying SS7 links, or else used for backup purposes. However, the cost of backhauling SS7 traffic can become quite expensive.
Subscriber Line Unit Extension
Connecting Remote Line Subscriber Unit (RLU) to a Class5 switch can be an issue in areas where no terrestrial transmission facilities are available. Using Satellite transmission or Troposcatter (http://www.comtechsystems.com/troposcatter.php) systems can provide solutions, but they come with some limitations:
Memotec's DCME systems are the solution to overcome those issues.
As a result of recent natural disasters such as the Katrina storm in US and the Southeast Asia Tsunami, telephony operators are facing increasing pressure by government and regulatory bodies to provision solutions for disaster recovery.
Mobile DCME: A Solution for Reducing Costs, Increasing Capacity and Migrating to 3G
Catering to Mobile Operator's NeedsCellular networks deserve a dedicated voice compression solution when it comes to optimize A and E trunks. That's because, unlike telephony networks, cellular networks already operate with compressed voice on the Radio Access, Network -RAN- and carries a good proportion of data traffic (Signaling, IN, SMS, HSCD, GPRS/EDGE user traffic) in addition to voice traffic.
Therefore, operators will require specific features not found in traditional telephony DCME products.
Memotec understands Mobile Operators dedicated requirements and has designed a Mobile DCME solution with a unique feature set that takes care of the Mobile Operator's network specific issues. The result is enhanced quality of service, uncompromised flexibility and maximum cost efficiency.
Voice quality is a primary and legitimate concern for Mobile Operators when introducing voice compression equipment. Because voice is already compressed in the RAN, voice traffic will likely undergo four and more compression-decompression cycles: example, a mobile-to-mobile handset communication, being hair-pined to the MSC over a compressed BSC to MSC A link. This results in severe voice quality degradation -delay, information loss-, while voice quality is a key competitive service differentiator between Mobile Operators. This further deteriorates if the A links is going over satellite, because of the added delay of satellite transmission.
Memotec is well aware of those issues, and offers a specific Mobile DCME solution that minimizes voice quality degradation over compressed A/E links down to a level unnoticeable to the end-user.
Choice of the voice codecMore important than the compression ratio performance is the resulting quality (MOS score) of the DCME codec combined with the GSM compressed voice. This can be significantly different from the codec's nominal MOS score (See codec and voice quality). Memotec 's DCME uses a toll-grade voice codec -G.729- which offers a better voice quality when used with longer transmission delay lines (satellite links, mobile applications) and in tandem operation with GSM codecs, while providing a good native compression ratio (8:1). Memotec then improves the compression ratio through silence suppression and pre-emptive bandwidth management techniques, resulting in an impressive 12:1 up to 16:1 compression ratio.
Transcoder Free Operation (TFO)Memotec's proprietary voice trunking protocol delivers an end-to-end single voice compression/decompression cycle, whether the voice is carried over multiple satellite hops or a combination of satellite and terrestrial transmission links supporting Memotec's DCME voice compression equipment. This applies in particular when the traffic is hair-pined on the same compressed A link (local call). Therefore, the maximum number of compression cycles supported by the voice traffic along a mobile-to-mobile connection in a Mobile Operator network using Memotec DCME solution will only be three, of which two occur at the RAN (GSM codec). Memotec's TFO feature guarantees that the voice quality will not be further deteriorated by going through unnecessary additional compression cycles.
Echo cancellationThe quality and performance of the echo canceller is instrumental to the overall voice quality experience enjoyed by the end-user, in particular if the link is going over long latency satellite links. Memotec has drawn upon its longstanding experience in providing voice compression solutions over satellite network to implement a trusted, best of breed echo canceller, which has won multiple awards and praises from its customers for the voice quality. It also provides up to 64ms echo tail, enough to match any network configuration and situation.
AMR codecWith the introduction of AMR codecs, TFO becomes a native function of the GSM codec right from the handset. This means that mobile-to-mobile communication will only be compressed once. The compressed voice traffic passes through transparently the TRAU located at the BSC or the MSC. It is then carried on the A and E link and switched at the MSC in compressed format. This requires the Mobile DCME to be able to pass through AMR voice traffic transparently, and to recognize and extract the AMR traffic from the 64 Kb/s digital channels (DS0) of the A/E voice trunks in order to gain some bandwidth efficiency.
V110 ServiceEarly GSM relied on V110 to provide a PSTN-like in-band data service to mobile users. This still applies to FAX communications and data services not using GPRS services. V110 offers mobile user a 9.6 kb/s data service , which is rate-adapted using bit stuffing technique to the transport channel (64Kb/s on a A or E link). Therefore, a Mobile DCME needs to be able to pass through transparently V110 data services. In order to maintain the bandwidth reduction performance objectives (12:1 or 16:1), it needs also to remove the V110 bit padding, then extract and carry only the 9.6 Kb/s useful data information.
Data interfacesMobile communications are not just about voice. Data services play also a key role in the service offering (SMS, IN services, GPRS and EDGE user data services). The transmission link between the BSC and the MSC, or between MSCs, also needs to carry this data traffic. Therefore, a Mobile DCME solution must not only carry and compress voice but also the various data services and interfaces present at the MSC or the BSC. This implies being able to aggregate, multiplex, optimize and compress SS7 traffic, GPRS/EDGE traffic at the Gb (BSC) or Gn (MSC /SGSN/GGSN) interface, and IP traffic.
Memotec's DCME solution offers a wide range of Serial, Frame-Relay, Ethernet, IP and ATM interfaces which can handle the many types of physical interface, protocol and speeds found in Mobile networks at the BSC, SGSN/GGSN, MSC and IN equipment. It also provides loss less line-rate hardware data compression, delivering up to 60% bandwidth reduction. A sophisticated SS7 traffic optimization algorithm (FISU frames filtering and PCR mode MSU spoofing on satellite links) enable Memotec's DCME solution to offer an additional 4:1 up to 8:1 bandwidth reduction on SS7 links.
Abis/Ater and A/E traffic mixWhile the hierarchical layout of the different link interfaces (A/E/Ater/Abis) of a Mobile Network is straightforward, real world implementation issues often blur this model: regulatory issues, traffic growth, available office and transmission facilities require to locate or co-locate BSC and MSCs at given locations. Consequently, flexibility is required:
â€¢ A given transmission link between two facilities might carry A or E traffic as well as Ater traffic;
â€¢ Upon traffic growth pressure, an Ater link may become an A link;
â€¢ Regulation may impose to drop-off PSTN traffic locally at a BTS (Abis) or BSC (Ater) location.
Memotec's DCME solution provides a complete GSM links optimization solution into one box: the same equipment can aggregate and optimize/compress Abis, Ater and A/E traffic on the same transmission media. The result is maximum network design flexibility for the operator, cost savings (one equipment/one solution), and capital preservation (no forklift upgrade when the switching the type of link: just a configuration change).
ScalabilityRapid, exponential growth is a characteristic of Mobile networks. Everyday roll out of new services also calls for always more bandwidth. The ability to scale is then key to any system deployed in the network.
Memotec's DCME offers Mobile Operators the most versatile and flexible solution with a range of products that start from as low as one or two T1/E1 trunks and can scale up to 32 voice trunks without forklift upgrades. With Memotec, Mobile Operators don't need to pay the premium attached with large systems, while preserving scalability in a true "pay-as-you-grow" fashion.
Satellite (or leased line) A or E Link Cost Reduction
Many mobile operators who have deployed satellite A or E links are still carrying voice as plain PCM (G.711) 64 kbit/s channels or ADPCM (G.726) 32 Kbit/s channels, while SS7 64 Kbit/s signaling traffic is passed through transparently. The main reason for this is the fear of degrading voice quality by using more aggressive voice codecs. However, as demand for more capacity increases and customer ARPU decreases, the cost of carrying voice trunks over satellite becomes a heavy burden to the Mobile operator OPEX.
PDH Microwave link (or leased line) congestion.
Microwave links are routinely used by Mobile Operators, as an inexpensive alternative to fiber for connecting remote regions. However, PDH microwave systems are limited to 34 Mbs or 16 E1s capacity, which can come short as traffic increases. Upgrading the microwave links to SDH is quite a costly solution, and takes time, as the whole microwave chain including repeaters needs to be changed (forklift upgrade).
Ater to A link migration
In an Ater link configuration, the TRAU (Transcoding Unit) is located at the MSC, and voice information is carried between the BSC and the MSC in a compressed format (usually 16kbit/s per voice channel). But as traffic increases with market share and penetration rate, it might become necessary to locate the TRAU at the BSC, thus migrating the Ater link to an A link. Voice being uncompressed in an A link, it occupies a full 64 kbit/s circuit as opposed to 16 or 8 kbit/s in an Ater link: an A link will require at least 4 times more transmission capacity than an Ater link, thus significantly increasing network OPEX.
A/E Link Backup (disaster recovery)
A/E links are the critical lifeline of Mobile Operators, as they carry the bulk of the operator's business, i.e. voice traffic. Therefore, the transmission infrastructure supporting those links shall offer the maximum availability guarantees. For example, a PDH E3 (34 Mb/s) outage, carrying 480 voice channels, will cost the Operator near $3,000/hour of revenue loss (at 10c/mn).
In a typical MVNO (Mobile Virtual Network Operator) application, the Mobile Operator uses a third-party operator's RAN (Radio Access Network) to provide services to its customer base in a remote region under his own brand name. The third-party RAN is connected to the MVNO own network over A links (The MSC and HLR/IN servers are owned by the MVNO).