Definition of Technology

The application of science, especially to industrial or commercial objectives.

The scientific method and material used to achieve a commercial or industrial objective.

Electronic or digital products and systems considered as a group. . .

Anthropology The body of knowledge available to a society that is of use in fashioning implements, practicing manual arts and skills, and extracting or collecting materials. (Collected).

Cellular Technology

GSM Network Infrastructure:

The following figure depicts a typical GSM network (called, Public Land Mobile Network or PLMN) infrastructure.

Ref: Wireless Communications Systems and Networks, By Mullett, Thomson Publisher
Note: The solid lines are for user traffic plus control signalling, if any. The dotted lines represent
control/management signalling/messaging only.
AUC_Authentication Center
BSC_Base Station Controller
BSS_Base Station Subsystem
BTS_Base Transceiver System (Antenna System + Radio Base Station)
EIR_Equipment Identification Register (for IMEI verification)
IMEI_International Mobile Equipment Identity
FNR_Flexible Numbering Register (for number portability)
GMSC_Gateway MSC
HLR_Home Location Register
ISDN_Integrated Services Digital Network
IWF_Interworking Function
ILR_Interworking Location Register (for roaming between AMPS and GSM system)
IWMSC_Interworking MSC
MS_Mobile Station
MSC_Mobile Switching Center
NSS_Network Switching Subsystem
OSS_Operation and Support System
PDN_Public Data Network
PSTN_Public Switched Telephone Network
SMS_Short Message Service
VLR_Visitor Location Register

Antenna diversity on smart technology

Diversity – What’s Diversity?

1. Receive diversity provides an effective technique for both overcoming the impact of fading across the radio channel and increasing the received signal to interference ratio.

2. The former is achieved by ensuring “uncorrelated” (i.e. low enough correlated) fading between antenna branches i.e. not all antennas experience fades at the same time.

   Using antenna arrays for diversity reception is one of the most straight forward uses of antenna arrays. Because the power level of a received signal can vary significantly with small changes in distance, a diversity array simply uses a set of antennas and combines the signals to obtain the maximum signal.

 

Kinds of Diversity:

1. Time diversity                                

      Coding, interleaving

2. Frequency diversity

      Frequency hopping

3. Space diversity

      Multiple antennas

4. Polarization diversity

       Dual-polarized antennas

5. Multi-path diversity

       Equalizer

How the Diversity Antenna Works:

Reflections and Multipath Signals
When a modem is in line of sight with a tower, it receives a main or incident signal from the tower. However, because of the properties of radio propagation, the modem also receives many reflections of this signal as the signal bounces off of buildings, mountains and other structures. Depending on the angles that the reflection or multipath signal comes from, it impacts the reception of the incident wave – for the better and the worse. This can be seen in the diagram where the signal is very good and poor. When the reflections cause a negative impact (signal fading), this causes signal strength reception in the modem to decrease and therefore impact the performance of the data transmission. At the right angle, it can also add to the performance of the signal. Reflections and Multipath are present in all cellular technologies (1X-RTT, EVDO, HSDPA, etc.).

Using a Diversity Antenna for Better Performance
By using a second antenna that is optimally spaced from the main antenna, space diversity can be achieved. This is the situation when one of the antennas is being negatively impacted by multipath signals; the other antenna is being positively impacted by the same situation. This can be seen in the second diagram. In this case, the modem will receive the better of the two antennas reception, thus achieving better signal strength over time.

Optimal Installation of the Diversity Antenna
To get the best performance, the Diversity antenna should be placed at a minimum of 1 and 5/8 of a wave lengths away from the other antenna. Therefore, the minimum spacing for antennas in the 800 MHz frequency is 1 5/8 * 13.5” = 22”. The diversity antenna can be spaced further away than this, ideally in increments of 13.5”. Therefore, 22”, 35”, etc. For a 1900 MHz only network, the optimal distance would be 1 5/8 * 6.2” = 10”. 

Cellular Mobile Technology

1. Frequency modulation

2. Antenna diversity
3. Cellular concept
4. Bell Labs (1957 & 1960)
5. Frequency reuse
6. Typically every 7 cells
7. Handoff as caller moves
8. Modified CO switch
9. HLR, paging, handoffs
10. Sectors improve reuse
11. Every 3 cells possible

Definition of Technology

The application of science, especially to industrial or commercial objectives.

The scientific method and material used to achieve a commercial or industrial objective.

Electronic or digital products and systems considered as a group. . .

Anthropology The body of knowledge available to a society that is of use in fashioning implements, practicing manual arts and skills, and extracting or collecting materials. (Collected).