We spend quite a lot of time at WhichVoIP talking about Mobile VoIP which of course runs on cellular phones. For today’s blog post we thought we would turn our attention to cellular technology. When talking about cellular, there are two major forms of underlying infrastructure that define how cellular signals are broadcast around the globe. This technology is transparent in regard to the end user experience, for the most part. Different providers have adopted both GSM and CDMA into the mainstream for cellular usage.
For most of the world, excluding North America, cellular networks are built on the Global System for Mobile Communications or GSM. This network originally designed in Europe was created to replace the first generation (1G) analog network. In 1987, 13 countries collaborated at Copenhagen, Denmark to agree on a standardization for international communication standards. Eventually this was absorbed into the ETSI which lead to a formal publication release in 1991. By 1993, the first GSM network was operational in the UK.
You can think of GSM along the same lines of a physical TDM network. On a basic premise, this means that data is transferred digitally where information is simultaneously sent and received on a single channel. The devices on these networks scan for the nearest cell antenna in the area to transmit and accept information. These cells come in a variety of sizes and strengths which offer application for different kinds of environments such as sprawling rural areas or urban settings that have many obstructions.
North America has a little different take on overall cellular implementation compared to the rest of the world. Though AT&T and T-Mobile use GSM, the rest of the major carriers use phones that rely on the multiple access process of multiplexing that sends information simultaneously over a single communication channel. The concept was first conceived by Russian scientist Dmitry Ageev in 1935. The technology was first used by Leonid Kupriyanovich in 1957 with a phone called the LK-1.
In regards to the transmission of radio frequencies, CMDA works a little differently compared to GSM networks. GSM uses a more simplified manner of transmitting data in full duplex where two devices that are connected point-to-point communicate using a full duplex along the channel. CDMA spreads the bandwidth of data across a spectrum of frequencies that falls into the same frequency domain. This requires each transmitter to use a specific code for transmitting on the network which is used by the other endpoint that identify where the data falls in the spectrum. This signal data is transmitted along with the information (i.e. voice or messaging) sent during the transmission, though at a much faster rate to allow the device to find the correlating (fun fact: the original devices from the 50s were known as correlators) information. Each channel is used for a short time which prevents interference with other signals.
Which is better?
When CDMA first arrived on the scene, it was much better than the GSM networks of the day. When companies like Sprint switched from analog to digital starting in 1996, CDMA was the superior technology. It was faster and offered more capacity. Today, GSM has caught up allowing just as much data to be transmitted over the network.
The two broadcasting technologies have been competed for attention in the US since the rollout of CMDA networks, which eventually took over as the most widely used method of transferring data. It could be argued that GSM has actually surpassed CDMA as far as functionality is concerned, especially in terms of security. Though both kinds of broadcasts could be easily intercepted, GSM has added encryption to the service which has made these transmissions much more difficult to decipher, particularly because of GEA/3 and higher encryption.
To answer the question in the heading: I feel GSM is currently better than CDMA but it’s a debatable topic. Though encrypted GSM communications can be broken, the RC4 encryption used by CDMA are much easier to crack. This is essentially the same technology used by WEP encryption of older wireless network routers.
Verizon – changing it up with LTE
The US has been CDMA based for roughly a decade, thanks largely in part to the efforts of Verizon. However, Verizon is now focusing on providing a purely VoIP solution to their customers via LTE. The infrastructure is finally laid for this switch and the provider is just about ready to make a total shift.
As the current CMDA network in place is already quite effective, making this switch will change the way devices are manufactured. Currently phones have dual radios built in allowing the device to connect to the voice network as well as the data network concerning phones that are LTE enabled. If customers were to only have LTE at this moment in time, issues would arise when connecting to older 2G and 3G networks until other carriers shift to this new infrastructure.
As of last year, the company Qualcomm who developed the chipsets for the first CMDA phones successfully passed LTE calls to both 2G and 3G networks. This means that since the infrastructure is mostly complete, Verizon can start to roll out phones that are purely LTE. Finally, Verizon customers can rejoice as they will have a battery life on par with other providers who offer the same phones.