Worldwide fixed and mobile traffic is exponentially increasing every day. The usage of services like video, p2p, tv on streaming, gaming and mobile data through laptops and handheld devices is growing up day by day.
A telecommunication system model consist on three main parts: the transport network (core network), the access network and the terminal. There are a lot of transport protocols and networks, although IP is the most widely used nowadays. In the case of Access networks, we use many wireless and wired technologies. Most common wired technologies are ADSL and RDSI, whereas most common wireless technologies are WLAN, Cordless, satellite and cellular communications which includes GSM (2G), GPRS (2.5G), EDGE (2.75G), UMTS (3G), HSPA (3.5G), HSPA+(3.75G) and LTE(4G).
GSM is a standard set developed by ETSI for digital cellular networks. Currently there are several bands used for GSM; for example, in Spain, we use 900MHz and 1.8GHz bands. The standard defines a full duplex system with 125 radio channels for uplink and 125 radio channels for downlink with a separation of 45MHz between them. Each channel has a bandwidth of 200kHz and supports 8 users simoultaneously.
GSM was designed to allow phone calls between users and because of that better telecommunication standards have been developed to allow data transmissions.
GPRS is the evolution of GSM to transmit data in packet mode (GSM use circuit mode) over GSM architecture. It takes advantage of the GSM infrastructure and adds two new nodes (SGSN and GGSN) to deliver data packets. Moreover, terminals support both services: class A (simultaneously GPRS and GSM), class B (GSM priority over GPRS) and class C (GPRS or GSM).
Another improvement of GPRS is that it allows to assign different Qualities of Service to different mobile users depending on the throughput, the delays and the reliability.
GPRS evolves to EDGE to enhance the bitrates and the data throughput using 8-PSK modulation. As a result of this new modulation and without changing anything else, GPS multiply by 3 the modulation bit rate and as a consequence, the user data rate.
3rd Generation of mobile communications was developed to support a strong demand providing more throughput and new services. These improvements have been achieved through a technical, network and service evolution.
UMTS was developed to use IP for all the interactions and communications and, because of that, new architecture, protocols and standards have been designed. UMTS use CMA modulation with carriers of 5MHz in FDD and TDD. Moreover, new radio access has been designed and new QoS have been defined depending on the services (voice over IP, video streaming, videoconference, mail, web…).
UMTS systems have been enhanced with HSPA in order to improve the packet data performance. HSPA consists on two components: HSDPA (Downlink HSPA) and HSUPA (Uplink HSPA). This system use many techniques to enhance the throughput and minimize the delay: MiMo techniques, physical layer retransmission, fast cell selection, adaptive modulation and coding, scheduling for uplink…
HSPA+ provides an evolution of High Speed Packet access and provides data rates up to 84Mb/s on the downlink and 22Mbit/s on the uplink. These bitrates are got thanks to the usage of a multiple antenna technique (MIMO), higher order modulation (64QAM) and combining multiple cells into one with a technique as Dual-Cell.
New technologies are developed to increase the spectral efficiency, which means upgrading the phased existing systems and deploy new wireless technologies. LTE is designed to deliver significantly higher levels of capability and performance and it will coexist with 3G networks. Moreover, LTE is scalable and introduces a new radio interface technology based on OFDM providing peak data rates of 300Mb/s (downlink) and 7Mb/s (uplink).
Nowadays main operators are migrating from 2G and 3G networks to 4G. LTE will initially be deployed in urban areas and then will be extended. Although LTE is able to co-exist with at least 15 other networks because of his flexibility, gradual migration of cellular services is taking place.