DSCH - Downlink Shared Channel

The Downlink Shared Channel is a downlink transport channel that may be shared by several UE (User Equipment). It is used to carry dedicated control or traffic data from the SRNC/BTS (Serving Radio Network Controller). The DSCH will be associated with one or several downlink DCH (Dedicated Channel).

GSM Technology

What is GSM?

GSM (Global System for Mobile communications) is an open, digital cellular technology used for transmitting mobile voice and data services

The origins of GSM can be traced back to 1982 when the Groupe Spécial Mobile (GSM) was created by the European Conference of Postal and Telecommunications Administrations (CEPT) for the purpose of designing a pan-European mobile technology.

It is approximated that 80 percent of the world uses GSM technology when placing wireless calls, according to the GSM Association (GSMA), which represents the interests of the worldwide mobile communications industry. This amounts to nearly 3 billion global people.

GSM supports voice calls and data transfer speeds of up to 9.6 kbit/s, together with the transmission of SMS (Short Message Service).

GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and 850MHz bands in the US. The 850MHz band is also used for GSM and 3G in Australia, Canada and many South American countries. By having harmonised spectrum across most of the globe, GSM’s international roaming capability allows users to access the same services when travelling abroad as at home. This gives consumers seamless and same number connectivity in more than 218 countries.

Terrestrial GSM networks now cover more than 80% of the world’s population. GSM satellite roaming has also extended service access to areas where terrestrial coverage is not available.

What is CDMA2000 1xEV-DO

EV-DO is a high-speed network protocol used for wireless data communications, primarily Internet access. EV-DO is considered a broadband technology like DSL or cable modem Internet services.

Certain classes of cellular phones support EV-DO. These phones may be available from various phone carriers around the world including Sprint and Verizon in the U.S. Additionally, various PCMCIA adapters and external modem hardware exists to enable laptops and handheld devices for EV-DO.

The EV-DO protocol uses asymmetric communications, allocating more bandwidth for downloads than for uploads. The original EVDO Revision 0 standard supports up to 2.4 Mbps data rates down but only 0.15 Mbps (about 150 Kbps) up.

An improved version of EV-DO called Revision A increases download speeds up to 3.1 Mbps and uploads to 0.8 Mbps (800 Kbps). EV-DO providers have gradually been upgrading their equipment from Rev 0 to support Rev A.

A future version of EV-DO called Revision B (not yet widely deployed) promised to offer much higher data rates as this protocol is capable of aggregating bandwidth from multiple wireless channels. Early trials have achieved EV-DO Rev B downloads of greater than 9 Mbps.

As with many other network protocols, the theoretical maximum data rates of EV-DO are not achieved in practice. Real-world networks may run at 50% or less of the rated speeds.

CDMA2000 1x EV-DO cell phone system is a standard that has evolved from the CDMA2000 mobile phone system and it is now firmly established in many areas of the world. The letters EV-DO stand for Evolution Data Only or Data Optimised. From the title it can be seen that it is a data only mobile telecommunications standard that can be run on CDMA2000 networks.

The EV-DO cell phone system is capable of providing the full 3G data rates up to 3.1 Mbps now that release A of the standard has been issued. The first commercial CDMA2000 1xEV-DO network was deployed by SK Telecom (Korea) in January 2002.

EV-DO Basics

• EV-DO - Evolution Data Optimized
• Personal broadband wireless service for a wide range of customers, from business people to students
• Always on - - similar to DSL (wherever 3G capability is available)
• Rides on CDMA signal- 1x data capability available everywhere CDMA voice service available
• Up to 10 times the peak data rate of the next best public wireless solution - 800 - 1,000 Kbps (kilobits per second) average download speeds, comparable to DSL speeds
• Allows the user to be connected herever they are are not only for email, but for downloads, large files, photos, spreadsheets, etc.
• Advantages over WiFi:
• Always on with seamless roaming!
• Signal can travel on same cell sites as cell phones
• No 300-ft range from the cell tower or "hotspot"
• Customers can access their corporate VPN (virtual private network) anywhere they can get a cellular signal via a secure, encrypted signal
• Can download and run video clips in real time
• Can provide service to customers outside of cable-modem or DSL areas
• Relatively low cost with high capacity - allows rich web browsing and application usage
• 1xRTT: 50Kbps - 100Kbps Upload and Download (bursts to 144Kbps)
• EVDO Rev 0: 400kbps-1000kbps Download (bursts up to 2.0Mbps), 50kbps-100kbps Upload (bursts to 144Kbps)
• EVDO Rev A: 600Kbps-1,400Kbps Download (bursts to 3.1Mbps), 500Kbps-800Kbps Upload (bursts to 1.8Mbps)

What are Femtocells?

Femtocells are low-power access points that can combine mobile and Internet technologies within the home. The femtocell unit generates a personal mobile phone signal in the home and connects this to the operator’s network through the Internet. This will allow improved coverage and capacity for each user within their home.

Femtocells have an output power less than 0.1 Watt, similar to other wireless home network equipment, and will typically allow up to about 4 simultaneous calls/data sessions at any time. Mobile phones connected to a femtocell will typically operate at levels similar to other wireless phones used in the home.

Femto cells or femtocells are small cellular telecommunications base stations that can be installed in residential or business environments either as single stand-alone items or in clusters to provide improved cellular coverage within a building. It is widely known that cellular coverage, especially for data transmission where good signal strengths are needed is not as good within buildings. By using a small internal base station - femtocell (femto cell), the cellular performance can be improved along with the possible provision of additional services.

In order to link the femtocells with the main core network, the mobile backhaul scheme uses the user's DSL or other Internet link. This provides a cost effective and widely available data link for the femtocells that can be used as a standard for all applications.

There are many advantages for the deployment of femtocells to both the user and the mobile network operator. For the user, the use of a femto cell within the home enables far better coverage to be enjoyed along with the possible provision of additional services, possible cost benefits, and the use of a single number for both home and mobile applications. For the network operator, the use of femtocells provides a very cost effective means of improving coverage, along with linking users to their network, and providing additional revenue from the provision of additional services.

Although there are advantages and disadvantages to the use of femtocells, their use has many advantages for both user and network provider.

Typically, a single femtocell will deliver voice services simultaneously to at least four users within the home, while allowing many more to be connected or ‘attached’ to the cell, accessing services such as SMS. Additionally, femtocells will deliver data services to multiple users, typically at the full peak rate supported by the relevant air interface technology, currently several megabits per second and rising to tens and hundreds of megabits per second in the future. But by removing the capacity hungry indoor mobile users from the outdoor network, femtocells also in effect improve performance for consumers outside. Indeed, for each additional indoor femtocell user, system resources are freed to serve about ten outdoor users. The femtocell behaves like a normal base station in that as users enter or leave the home their voice or data services are seamlessly handed over from or to the outdoor network as required.

Subscribers benefit from perfect cellular coverage and faster mobile broadband in the home as well as a more competitive voice and data tariff. Operators get optimum cellular coverage and more mobile usage in the home and dramatically reduced operating costs especially through backhaul - their single largest OPEX - and power savings. Equally importantly the cellular operators’ capital expenditure will significantly drop because accelerating data usage means they will inevitably have to heavily invest in their outdoor network in terms of new cell sites and backhaul to meet expected demand - something femtocells do at a fraction of the cost. In fact, Paul Jacobs, Qualcomm’s CEO, recently said that the gains in throughput available to femtocell users are “equivalent to that brought by the cell phone’s shift from analogue to digital.”

Finally, as mobile operators look beyond 3G to LTE or WiMAX, femtocells offer a new, dramatically lower-cost model for network rollout. For example, LTE femtocells could be employed using higher frequencies to deliver targeted intense high bandwidth requirements inside buildings - exactly where subscribers most demand it. Operators can then use their existing networks outdoors as demand slowly builds up and then use the scarce lower frequency spectrum to provide good quality LTE coverage across entire markets with the minimum number of outdoor network cells. As we have seen, the simple proposition of lower costs, for both operators and consumers, combined with improved coverage and services is compelling. Yet there are also challenges which must be overcome before widespread commercial deployments can become a reality.