Sprint Airave -- first U.S carrier offering of femtocell technology?

[thuor]

Check out the following link from Sprint/Nextel http://airave.sprint.com/

Just a brief description of what the Sprint Airave is and a comparison (technology only no pricing comparison) with UMAN technology such as T-Mobile @Home ....

The Sprint Airave can be viewed as a mini BTS (base trasceiver station) that resides in the customers premises (sounds like an oxymoron to have a Basestation CPE but yup!) and provides up to 5000 sq Ft of NLOS cellular voice and data coverage. The hardware that sprint is currently trialing in Indianapolis and Denver (as of August 2007 with full launch slated for 1Q, 2008) is a Samsung Ubicell femtocell. The samsung Ubicell is available in CDMA 850 and 1900MHz (which is what Sprint uses) as well as WCDMA (for traditional GSM carriers -- no offering in the U.S yet).

This device/service is very similar to T-Mobiles @Home UMAN (Unlicensed Mobile Access Network). Most notable difference in my opinion is really the authentication & multiuser access provisions, air interface and handset support. T-Mobile @Home allows any number of concurrent users (limited mainly by WiFi limitations) and each user may be allowed/denied access using regular WiFi security features WEP, WPA etc. On the other hand Sprint Airave is limited to 3 concurrent users and user access is based on the Sprint phone number. T-Mobile at Home UMAN uses a WiFi air interface to connect the handset to the CPE wheras Airave uses Cellular frequency band. This leads to one major positive thing about Sprint Airave in that it allows any CDMA handset to be used since the phone does not need any special chipset as does the T-Mobile @Home that requires a phone with UMAN/WiFi RF & baseband chipsets (such as the Nokia 6086, Samsung T409, Blackberry Curve).

Both the T-Mobile @Home UMA and the Sprint Airave Femtocell allow seamless handoff between the CPE and the Cellular Basestation. Currently there's no handoff between Samsung Ubicell devices in the Airave service but for T-Mobile @Home handoff can happen from CPE to BTS and viceversa and between CPE's. The Ubicell can also support CDMA200 1xRTT, EVDO although the Airave just has support for 1xRTT.

The Samsung Ubicell also has integrated GPS. This is most likely for E911 service as well as to probably allow for Sprint to control where device is used due to market licensing agreements with affiliates.

Basically the Airave just like the T-Mobile @Home and other such RAN (Radio Access Network) technologies are a win-win for the Carrier and the Subscriber. For the carrier they offer increased cellular voice and data capacity and coverage at a reduced capex & opex and offer scalable & rapid deployment possibility whereas for the user the move to an IP based backhual of cellular traffic means lower cost per minute of use (typically unlimited minutes for low cost). This is how carriers will overcome the capacity limitation often sited by 4G oponents. Will be interesting to see how Sprint integrates this with its WiMax offering (branded Xohm).

[thuor]

Availability of sprints Airave

Click here to check availability in your zipcode: http://airave.sprint.com/availability.aspx

Also one question that we keep getting is when one should use high gain cellular antennas and/or cellular repeater/amplifiers and when femtocells such as the Sprint Airave make sense. Often this arises out the the misunderstanding that both do the same thing. Note however that for cellular amplifiers and high gain antennas to be effective you MUST at least have a usable signal (i.e a signal above the receiver sensitivity of the amplifier whose work it is to boost it above the receiver sensitivity of the phone or datacard i.e signal stronger than roughly -150dBm). If signal is below noise floor or non-existent then no high gain antenna or amplifier gain can redeem you. Femtocells work where there is not signal at all since the femtocell acts as the "base-station" and connectivity to Sprints cellular network happens using the Internet.

[thuor]

Macrocell, Microcell, Picocell, Femtocell .......???

Biggest confusion is usually between Picocell and Femtocell so an explanation of all follows:

Basically all do the same thing i.e they are "cells".

Macrocell:
These are the big cellular towers we see when driving down the road. Consumer lots of power and require leased or owned land, operationg expenses for power, cooling, security etc Their high power requirement have carriers woeing over FCC mandate of 8 hour backup power since can only achieve this with diesel generators or fuelcells. Capex around $100K + monthly opex.

Microcell:
These are much smaller usually in urban areas where theres a high density of users. Many times they reside in leased rooftops. Capex around $20K + monthly opex

Picocell:
These are small indoor access point basestation CPE usually deployed by large enterprises and usually for backup. Usually integrators such as RfWeL deploy these rather than cellular carriers. Capex around $2K w/ very limited maintenance.

Femtocell:
Lowest in the food chain; small indoor access point base station CPE. Low power and low cost. Capex in the $200 range and virtually NO opex.

[sprintsuser]

Sprint offers me the hardware for free because I am out of the contract, and have poor coverage in my primary residence. So far, I am very happy about this device and Sprint's sincere effort to retain my business.

The only issue I have is that whenever I leave the Femto cell coverage, my phone will appear coming back into Sprint service area from roaming. The phone would go through the "search for signal" cycle, and then "enter Sprint service area." If I am in a call at the time, I would lose the connection.

I thought that Airave could do calls handover to the base station. I am not sure if I need to configure the phone in certain way.

[thuor]

Most likely reason for this is that the received signal strength (RSS) at the edge of your airave coverage is not sufficient for a clean handover to the macronetwork base-station which could happen even if when you do disconnect you are able to reconnect at the exact same location.

To my knowledge there's really no parameter you can set on your phone or on the femtocell device to change the RSS thresholds for handover. One big factor affecting the CDMA soft handoff mechanism is the phones receiver sensitivity which is a function of the specific cellphone analog RF circuitry. So a nice way to check this is by trying to use a different (higher performance = better receiver sensitivity) cellphone and seeing if you obtain the same results. The receiver sensitivity simply determines the weakest signal a radio can receive reliably at a predefined bit-error-rate which is why you sometimes find one phone dropping calls while another phone in the same network and location connecting fine.

Now one other thing that occurs to me is that if you have sprint macrocellular coverage outside the coverage zone of your femtocellular coverage (even if weak) then it already means you can easily use cellular high gain antennas and cellular amplifiers/repeaters to boost your coverage. Here are generic drawings on how you would do this: http://www.rfwel.com/kc/application-drawings.php. This would allow you to connect at home without needing the femtocell (so you would be connecting to the macro network basestation) which means handover would be seamless (or not even required) when you drive away from your house.