Tuesday, March 15, 2011

Meeting Bit Error Rate (BER) for a design

SNR (Signal to Noise ratio) is related to BER such that higher SNR means lower BER. SNR margin is amount of additional signal loss that system can tolerate before BER increases above given level. SNR margin can be improved by utilizing DSP Adaptive filters to remove noise from signal. Adaptive filters are good for cancelling inter-Symbol-interference (ISI), echo, NEXT, FEXT.

Tuesday, March 8, 2011


UTRAN: UMTS Terrestrial Radio Access Network
UTRAN is a term comprising RNC, Base station describing 3G architecture.
UTRAN defines folling links:
lu: RNC to Core network connection
lub: RNC to eNodeB (Base station) connection
lur: RNC to RNC connection
uu: RNC to UE (user equipment) connection

Wednesday, February 23, 2011

4x4 MIMO

Systems with multiple antennas at the transmitter and receiver – also referred to as Multiple Input Multiple Output (MIMO) systems – offer superior data rates, range and reliability without requiring additional bandwidth or transmit power. By using several antennas at both the transmitter and receiver, MIMO systems create multiple independent channels for sending multiple data streams.
4x4 MIMO system supports up to four independent data streams. These streams can be combined through dynamic digital beamforming and MIMO receiver processing (in the red oval) to increase reliability and range.
The number of independent channels and associated data streams that can be supported over a MIMO channel is equivalent to the minimum number of antennas at the transmitter or receiver. Thus, a 2x2 system can support at most two streams, a 3x3 system can support three streams and a 4x4 system can support four streams, as illustrated in The figure below. Some of the independent streams can be combined through dynamic digital beamforming and MIMO receiver processing, as shown in the red oval, which results in increased reliability and range.
A Full-11n 4x4 MIMO system with dynamic digital beamforming and MIMO receiver processing supports two maximum-rate data streams, 99 percent of the time. Other configurations such as 2x2 and 3x3 MIMO are significantly less reliable, since they have fewer antennas and thus fewer extra spatial dimensions that can be combined.

Tuesday, February 22, 2011

Coexistence of Wifi & Femto Cells

What is Femto Cell:
Femto Cell is a small cellular base station, typically designed for use in a home or small business. It connects to the service provider’s network via broadband (such as DSL or cable). Lots of people face “low bar” problem in cell phones. This is due to reduced coverage in certain part of your home or even the whole area. Femto cells solves this problem by putting a cell base station at your location. Current designs typically support 2 to 4 active mobile phones in a residential setting, and 8 to 16 active mobile phones in enterprise settings. A femtocell allows service providers to extend service coverage indoors, especially where access would otherwise be limited or unavailable. Although much attention is focused on WCDMA, the concept is applicable to all standards, including GSM, CDMA2000, TD-SCDMA, WiMAX and LTE solutions.

Femto cells have been around for a while and finally the roll out is slowly picking up as Wireless Wifi connectivity is starting to slow down the traction of 3G/ 4G broadband services. Some people may yet debate the value of femtocells, but the tide has turned: in 2010, the number of femtocells around the world exceeded the number of macrocells, according to the Femto Forum.

Femtocells are small base stations that operators place in homes or businesses to improve coverage and capacity for users. While there is some debate yet about whether femtocells or Wi-Fi represents a better choice, most experts are now saying that the two technologies will work together.

AT&T has been rolling out Femto Cells in selective markets but with only voice services.Users can carry their femto cells if they travel anywhere. And if they leave their femto cells behind, they will be picked up by nearby cell towers/ BTS. But more and more service providers are starting to integrate Wi-Fi and Voice services in same base station so that end users can attach to the Wi-Fi network for data services and use the cellular connection for voice. Ubiquisys is one company that introduced new femtocells that include Wi-Fi during the conference.

It makes lots of economical sense to have femto for voice & Wifi for data services. But greedy network operators want to burden consumers with higher service charges in US, so roll out has been slow. Greed has often plagued telecoms & now celcomms for advancements in technology at even faster pace. That’s why open operating systems such as Android will open up the markets for increased competition, as web browsers did for Internet. Before I digress too much, Wifi is extremely important to bridge existing network infrastructure to voice networks and shatter Comms monopoly for consumers. Though Wifi offers cheaper existing Access Points (modems), Femto cells will burden consumers with additional cost of “yet another equipment” to buy or replace. Within 3G, consumers have been really unhappy over broadband requirements with Wimax or HSPA so far in 5MHz spectrum. Femto/Wifi combo can rescue carriers of shame.

Toward the end of last year, the number of femtocells in the U.S. reached 350,000, surpassing for the first time the number of macrocells. Globally, there are 1.7 million femtocells in use compared to 1.2 million macrocells.

The timing is right for even more growth of femtocells because many operators are upgrading their networks to LTE, the next generation mobile technology. At the same time they realize that users want to consume an increasing amount of data. Femtocells can help increase capacity for operators but deploying femtocells requires radio frequency planning. It's easier for operators to plan femtocells into new networks than it is to add them to an existing network.

Femto Cells also will break the trend of heavy leverage on LTE infrastructure & LTE Femtocells could roll out much sooner than previous generations. NTT DoCoMo is one operator that has been outspoken about working femtocells into its network upgrade plans, he said.

Femtocells can also help operators that are struggling with finding new sites for their base stations, an often expensive exercise. Femtocells are physically much smaller than a base station so can hang in many more kinds of locations. But at same time, Femtocells could encourage entrepreneurs to define new business models while breaking “Big Boys” operators.

Still, for some operators, sticking with Wi-Fi instead of femtocells makes sense. T-Mobile late last year said many of its Android phones would ship with software that allows people to use Wi-Fi to make phone calls and send SMS and MMS messages. Users can make Skype or Google phone calls using Wifi instead of using up their cell talk minutes. That offloads traffic from T-Mobile's cellular network and shifts the expense of backhaul to the Wi-Fi network.

The downside to using Wi-Fi currently is that users still have to actively turn on Wi-Fi on their phones before using it. But both Kineto and Ruckus talked about work going on internally and in standards bodies to make roaming between the cellular and Wi-Fi networks automatic. The confusion & technology use chunkiness will make these technologies harder for consumers to adapt.

Thursday, February 17, 2011

Mokia Phones are here, MoQuaKia around the corner

With Microsoft & Nokia strategic alignment announcement, a big wave is created for Win7 to be a noticeable player in mobile phone market. In 2010, Nokia announced Intel partnership to jointly develop Meego, which Nokia clearly is abandoning (not completely) with "Mokia" announcement. In 2009, Nokia announced mends with Qualcomm with Snapdragon chips in Nokia phones and since then Qualcomm has worked hard to optimize Snapdragon for Win OS as well along with Android. But till date there are no big announcements from Nokia for Snapdragon. Qualcomm story could be overplayed as all main mobile processors strive to optimize for both Win7 & Android, including Nvidia Tegra2, Texas Instruments, etc. Its a matter of time till we hear Qualcomm/ Microsoft/ Nokia - MoQuakia phones.

Mobile Phone Market Share

Mobile Market remains extremely competitive & landscape is changing constantly. Yesterday's market leaders are falling behind as market evolves.

Nokia still dominates the Revenue and Unit volumes in handset industry but competition is catching up.

Nokia, Apple, Samsung, RIM, HTC, LG, Motorola, and Sony Ericsson are controlling at least 5% market share

Mobile Telecomm Evolution



2G transition
(2.5G, 2.75G)




3G Transition
(3.5G, 3.75G, 3.9G)


LTE Advanced