Mobile Broadband Service » frequency

The key elements of LTE

engineer — Sun, 30 May 2010 04:20:36 +0000

Considering many benefit we can get especially the maximum speed, the implementation of Long Term Evolution will come soon in many mobile broadband providers. High latency is the most issue on current mobile broadband service and LTE technology can reduce it. To implement LTE technology, there some network element they should be prepared to achieve maximum benefit of LTE technology including back bone network from end user (BTS) to the core network and the international bandwidth from core network to internet gateway

There are some the key elements of LTE that should be implemented by mobile broadband provider while they plan to implement it:

1. OFDM (Orthogonal Frequency Division Multiplex) as the signal bearer

Orthogonal Frequency Division Multiplex (OFDM) is a form of transmission which uses a large number of close spaced carriers which are modulated with low rate data

2. OFDMA (Orthogonal Frequency Division Multiple Access)

3. SC-FDMA (Single Frequency Division Multiple Access).

OFDM (Orthogonal Frequency Division Multiplex) is being used in many other wireless internet service such as Wireless LAN (WLAN). OFDM is used in WIMAX service as well especially to broadcast technologies including DVB and DAB. OFDM has many benefits including its robustness to multipath fading and interference. Moreover even though, it may appear to be a particularly complicated form of modulation, OFDM lends itself to digital signal processing techniques

Meanwhile the OFDM signal, there are several option that possible to be chosen between three types of modulation:

QPSK (= 4QAM) 2 bits per symbol
16QAM 4 bits per symbol
64QAM 6 bits per symbol

There are several channels bandwidths that have been chosen for LTE are:

1.4 MHz
3 MHz
5 MHz
10 MHz
15 MHz
20 MHz

The modulation scheme that can be used by LTE is called SC-FDMA (Single Carrier Frequency Division Multiplex) which is a hybrid format. SC-FDMA combines the low peak to average ratio offered by single-carrier systems with the multipath interference resilience and flexible subcarrier frequency allocation that OFDM provides

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BSC – Base Station Controller

engineer — Fri, 21 May 2010 18:46:55 +0000

Mobile broadband service session and others telecommunication services when it reaches BTS than the session will be delivered to Base Station Controller (BSC) for the next process. Base Station Controller (BSC) is part of the telecommunication infrastructures more specific on the wireless network that control one or more Base Transceiver Station (BTS). Typically BSC could have ten or more BTS and they all controlled by this BSC. In the telecommunication architectures, BSC has several critical functions such as perform radio signal management for BTS and managing function e.g. frequency assignment and handoff.

Base Station Controller (BSC) is located between BTS and Mobile service switching centre (MSC). BSC provides the control function between both BTS and MSC. Beside handover function, BSC provides cell configuration data and control of radio frequency (RF) power level in BTS. When the data sessions from mobile broadband services and others service comes to BTS than BSC will allocate Radio resource to this session before they reach the application layer which located on the core network or out side (internet)

BSC is acted as a concentrator where many different low capacity connections to BTS with various traffic and services become reduced to a smaller number of connections to MSC. It means the session from mobile telecommunication subscriber which land on many BTS will be concentrated on BSC and than deliver it to MSC with a high level of utilization. You can imagine what happen if each of BTS with low level of utilization will connect to MSC directly. There will be many connections from BTS to MSC but has low traffic. This is not good telecommunication architectures and high cost. BSC is a bridge between both

Since the function is very critical on the telecommunication infrastructures either GPRS or CDMA, BSC should be installed be fully redundancy. The redundancy includes dual power supply, database etc. This redundancy will guarantee that the service will be not interrupted while the primary BSC is going down

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Failure points of wireless internet services

engineer — Fri, 04 Sep 2009 05:55:18 +0000

Wireless or mobile broadband internet service such as CDMA1x, GPRS, 3G or EVDO will have unstable connection. More subscribers they have, more often they will experience an unstable connection. The root cause of this problem could be anywhere depends on the capacity and occupancy of the network infrastructures. Generally, the point where wireless or mobile broadband internet service gets unstable connection could be;

Base Transceiver Station (BTS) capacity
Link utilization
International bandwidth capacity

While subscriber makes a data service on mobile broadband internet service session by dialing to the particular short code (for example #456) from their mobile phone or modem, BTS will allocate some resources for this session. Number of resources needed by data service session is bigger than voice or messaging (SMS) service. It needs around four times of voice resource. It means that if voice needs 64 kbps to make sure the calling session running well, data service (wireless or mobile broadband internet services) need 4×64 kbps. Meanwhile each BTS has limited capacity. Therefore, Telecommunication Company which has limited carrier frequency will assign first priority to voice and messaging (SMS) services rather than data service (wireless or mobile broadband internet services). There are many ways to resolve the capacity issue on the BTS side;

Assigning dedicated RF channel frequency for data service (wireless or mobile broadband internet services)
Different frequency between voice and data services (wireless or mobile broadband internet services)
Adding RF capacity by install more BTS

Traffic which requested by subscribers is huge internet traffic so then need high link capacity to carry out them. It different with voice and messaging (SMS) services which has certainty capacity then Telecommunication Company can predict how much link capacity to carry out this service. Meanwhile data service (wireless internet services) will has unpredictable traffic more often they will has huge traffic during peak hour. As the result, utilization link to carry out traffic from subscriber to Public Data Serving Node (PDSN) – suppose on the CDMA platform – will always getting saturated. Telecommunication Company will take some action to resolve this issue e.g.

1. Adding E1 capacity or

2. Migrate to optical network

International Bandwidth very expensive and usually Telecommunication Company will consider many times to add more bandwidth capacity. It could be that no issue found on the RF capacity and the link network but more often they will experience lack of international bandwidth capacity especially during peak hour while many subscribers trying to access internet on mobile broadband internet service

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