Ehsan Nourbakhsh’s Blog » review

Home eNB: Great Oppotunity for 3GPP LTE

Ehsan — Sat, 11 Apr 2009 02:38:01 +0000

In the recent years more and more wireless providers have started to provide femtocells to their customers. The customer can deploy the femtocell in any location that the coverage of normal towers are weak or absent. Consider a product like Samsung’s Ubicell. The user can plug this femtocell in their home internet switch, and use their regular cell phone to connect to the final service provider, e.g. Sprint.

E-UTRAN architecture from 3GPP document 36.300-880

As of December 2008, 3GPP documentation for Long Term Evolution networks has started to mention Home eNB as part of the Evolved UTRAN. This move can be a significant advantage for the final users, only if service providers fully recognize the extent of service this final addition can offer. This recognition might require a careful study of 802.11a/b/g Access Points, considering the similarities of the two products. Both these products are the front end of a network to final customers. While these final points are accessible to the customers, the actual network is not controlled by them.

Most APs initially were merely wireless transmitters, but they soon started evolving into more sophisticated equipments. The need to provide more functionality for the end user to adjust settings, e.g. channel or user access rules, resulted in simple interfaces to configure the AP. Currently wireless APs are commonly acting as firewalls, switches, DSL modems. But the true revolution for the APs happened when vendors such as Linksys started to provide open source firmware for their products. Because of the delay in this revolution, many golden opportunities are gone and we do not see as many diverse applications.

Given how larger organization such as universities might consider deploying a number of Home eNBs throughout their campus, there is a high level of interaction that would be only limited to these eNBs. As an example, in a university campus many calls and data interactions would be between students on the same area. Or consider an event like SXSW. While this year AT&T added enough resources to guarantee good coverage, smaller scale events do not motivate service provider to make such adjustments. Instead the organizing institute is well aware of the scale and the available resources and would be able to allocate more eNBs to the event area. One other aspect is access control: if I am paying for a Home eNB, I may not want my neighbor to user it for free unless it is an emergency call.

By providing good configuration options to the deploying organization, all sides of such scenario would benefit: the organization would enjoy faster service on their campus, the service provider would not have to worry about resource management and the manufacturer would ensure better sale of its products.

There are many challenges in providing such control to the final user. However, I believe the designers of 3GPP LTE have started taking initial steps and now the manufacturers need to move forward.

My Experience Buying A New Car

Ehsan — Sun, 27 Jul 2008 23:56:50 +0000

Recently I spent some time shopping for a new car. A dear friend of mine, Ahmad, recommended some good internet resources. These helped me find out how good was each deal that I got. He also helped me with some different issues in financing and mechanical/design things.

I will try to briefly explain the steps that I took, and how they were useful. As usual, it is just my experience. Verify everything and decide for your own. Here is a summary of links if you are in a hurry:

Read more about my experience using these links below…

Find out the price range

You need to decide: (a) how much down payment you can afford (b) how much you can pay each month, if you are looking for auto loan. Please note that buying a new car will change amount of monthly insurance and gas payment from what you spend now.

Once these two are decided for, you can estimate the final price of the car you are looking for. Some companies have reverse calculators. You enter monthly payment and down payment and they tell you what car and what total price you can buy. Honda has a simple tool here.

Later in the process I used software like Annual Percentage Rate Calculation Program. Better than that was a Excel sheet auto loan calculator. I used it to calculate some different prices that I guessed. I had these prints with me, and was able to catch an unannounced change in price in one dealership. Saved me $1000!

This step helped me narrow my search to a smaller number of models.

What make and models are close to my price range? Which of them have good reviews?

I looked at Consumer Reports annual special issue for new cars. They have classified cars based on price, quality, consumer satisfaction and other factors. I don’t know much about cars and their reviews were consistent with what my know-about-cars friend told me. I also asked a couple of friends who had recently bought cars. This narrowed my search to base model of Honda Fit and Nissan Versa 1.8S.

One important thing is to check which cars are going to be redesigned. If a car is redesigned next year, your new car will look “old” from the moment the new design comes out.

What options these model have that are useful for me?

Again, I consulted friends who had driven the same car before as well as online resources and Consumer Reports. Specially I liked the Edmunds’ Long-Term Road Tests Blog. Also, Edmunds has a step by step price estimator, during which you can select options and see the prices. In this step I decided I liked to have ABS and cruise control options in the Versa. Honda Fit did not have any option for the base model.

Also note that some options are always installed on cars. For instance most Nissan Versas that I saw have splash guard installed by default. I realized this when I checked inventories of Nissan dealerships in my area. You can either check their inventories from Nissan’s main website or local inventories. Also you can search third party sites like AutoTrader.com or Cars.com. My experience was the inventory of Nissan’s main website was not up-to-date. Also, the third party websites did not have all the details of options installed on the cars sometimes.

Talking with dealers and finding good deals

I tried getting online quotes from dealers through Nissan’s main website. The result was not so interesting. Then I tried using the third party websites and Edmunds.com. The ones I contacted using Edmunds.com were the ones I got good price quotes from.

After the initial quote, I had around 10 emails passed back and forth, negotiating the price. They made “mistakes” sometimes and quoted me the MSRP. I would remind them the fact that I have a better quote, and then they would correct their quote. Ahmad just reminded me that there is no need to mention you are getting financing from them before going to their dealership. In fact what I did was I would let them convince me that I needed the financing from them. This makes negotiating easier, as you still have the “upper hand” somehow.

I noticed, with Ahmad’s help, that Nissan had an incentive choice of either $1000 cash back or a %1.9 APR. Most dealers would give a price quote with the $1000 reduced. So when I mentioned I am getting the APR in the dealership, they would jump $1000 up. When getting quotes, ask them for quotes “before reducing any incentives applied”.

One good website to see the price quotes others get is the Edmunds forums. I usually searched Versa+paid+price in Google to reach the forum. The first result is usually the answer: http://townhall-talk.edmunds.com/WebX/.ef17997/ You can check the prices and see what is the good prices people get. This should be way lower than the MSRP unless the car is in high demand. In my case the MSRP was $1350 higher than the final price I paid. Worth the time, isn’t it?

Test drive, negotiate and buy

Test Drive: During the test drive I only tested how was the visibility and how I liked the shape of the car. Also I asked a friend to come with me, and before the test drive when the dealer was driving I would seat in the back seat and see how was the back of the car. After the drive I would write down the VIN number of the car.

Price: I usually would almost finalize a price over email with the dealer. Telephone price quotes are hard to prove and the dealer may claim there was a “mistake”. I would ask every detail, i.e. the VIN and the options and price before incentives, to be sent to me with email. Then I would take prints of the emails from all dealers when going to see a dealer. The prints are very useful for negotiating. I got a lower price from a dealer to “match the price” of another dealer, just by showing their printed quote. Also if you are trying to get an incentive that the main company provides, print that page and have it with you.

Buying: During the final buying step, I just made sure nothing other than what was agreed was there in the price break down, of course by mistake. Also, the accompanying friend told me that the “finance” person that I was supposed to talk after the dealer was in fact a sales person for the extended warranty stuff. “Just say no!”., he recommended. Go through the documents that you sign, take your time and check this is what you want. I also wrote the VIN number on the check for down payment, just in case.

This is my experience and I hope to update here in near future if I remember something more. Hope it helps you get a better price. Again, verify everything. I don’t share your car with you, and I don’t share the trouble either Good luck with your new car!

Google Maps Mobile “My Location” feature, how does it work

Ehsan — Sun, 06 Jan 2008 06:13:32 +0000

Google Maps mobile has been one of my favorite applications from Google. Recently they added one beta feature to it which is a milestone for the Google Maps Mobile (GMM). They have added the ability to find your approximate geographical location solely based on the data that your cell phone receives from base stations. This is really nice since once you know the approximate location, you can guess the details yourself. Also, each time you don’t need to enter your own address before searching for the destination address.

It has been an interesting case to find out how they do it, and by how I mean the general implementation idea and not the theoretical foundations. I post here my current understanding of the implementation, which may be lacking some parts. I hope I can update this as I gather more information.

Federal Communications Commission (FCC) requires that antenna structures with height over 200ft, or close to airport or with some specific slope requirements, register themselves. FCC publishes information gathered from these registrations on their website here. One can search these based on file number, location, address or many other criteria. For instance the tower inside UTD is shown here. The FCC File Registration Number (FRN) shown here is posted in front of the facility too.

Still one problem remains unsolved. FCC only registers the antenna structures, and not the Cell ID broadcasted by the radis on the tower. The only thing that your cell phone receives when it is connected to the radio is the Cell ID (CID) and Location Area Code (LAC), and not the FRN of tower. Although the LAC indicates an area location, the exact location and its boundaries are not broadcasted. If users wish to map the LAC to latitude and longtitude, they should find the mapping themselves. And to make things worse, phone companies do not publish these datasets of CID/LAC.

There have been multiple attempts by different parties to collect information from users of how a CID/LAC pair is related to geographical location. For instance the GSMLoc.org , CellSpotting.com and many similar projects try to gather this information from their users. Unfortunately I have not been able to find such project with enough data for users inside United States, while most of these projects cover good pars of Europe.

Google seem to have a database of the to location mapping, and seems to be completing it based on the data it receives from users. When you press the 0 button, your cell phone sends the pair(s) that it sees to Google’s server. The server comes up with an approximate location(the blue dot) and the possible error (the blue circular area). Obviously you need a data connection for the location info and the map images being sent and received. I don’t know if they have been able to buy parts of the database from phone companies, or how they use user queries to update the database, but whatever it is their final software rocks.

One final note, there are some software that can show the Cell ID and Location Area Code on your cell phone. I am using NiceTrack on Windows Mobile 2005 on my HTC Wizard. It also shows the signal strength as a graph. There are also similar software for different platforms. If you want to try the GSMLoc and CellSpotting projects, these can give you the pair.

Links for more information and resources:

Assisted Driving

Ehsan — Sun, 03 Jun 2007 09:51:36 +0000

It is very exciting to see real world applications of computer related technologies. It gives me hope that this field is actually doing work, as other fields of science do. One branch of such real world applications is “assisted driving. What I mean by assistance in here is providing information, such as current speed and location, as well as the path to go and the directions to follow at any moment.

Also, it might include information about road construction and traffic. Providing address and phone information about restaurants and hotels, as well as national parks and theme parks, close to current location is a plus.

Microsoft Streets & Trips

Microsoft Streets & Trips provides most of the above. I have been very happy about it in recent trips. It is really interesting that it really “worked” in real life situations.

Since it uses around 1GB of your hard driv, you do not need to be connected to the internet to have the road maps.
You can update the database online, with only a few clicks. The update includes road construction data.
It can provide driving directions to destination from current location. If connected to GPS device, it can locate itself and update the data based on that.

It can also give you accurate speed and direction, to avoid mistakes by driving in wrong direction.
In case your GPS device does not provide you with coordinates and signal strength, the Microsoft Streets & Trips does it on screen.
It can also read the directions loud so you don’t have to check the screen.
You can do a quick search about different types of hotels, restaurant and other public places around you based on the distance. It simply draws a circle around you, and by clicking on each resort it gives phone number and address to that place. It is really impressing, since you have this information not using web, but only from your local database.
You can plan for stops and specific route points. By specifying the start time and duration of stops, it can provide you an estimation of arrival and directions times.
It can also predict total gas price, based on miles and gas price!

The problems with Microsoft Streets & Trips?

It should be installed on a laptop, which is not very easy to take around in “your pocket”.
Limitations of laptop battery apply. It means either you should have spare batteries, or you should be able to plug it in. This means converter to car plug or only using at office/home.
It is not easy wise to drive and do the directions. If you are going to change route and find local place on the fly. There must be someone who does that, and you do the driving.

OnStar

The other approach that has cleared the disadvantages of the Microsoft Streets & Trips is OnStar service. This is really hardware dependent. It means you should already have the hardware installed on your vehicle. But, in return, it gives you more services, as the service operator can not only interact with yourself, but your car as well.

Once you have the hardware installed on your car and subscribed to OnStar, you can “call” the service provider by pressing only on button on your car’s rear mirror.

The operator can ask you where you want to go. No typing, no need to somebody else to do the route planning, you just speak. This is very comfortable even for computer professionals, and people who are not very interested to operate a device by themselves.
The operator can send the directions to your car’s audio system.
Your car “calls” the service operator if there is an accident. They can contact authorities in turn. The comfort it gives is really reassuring. I would buy such service for my mother if it was available in Iran.
You can ask the operator to open your car if you forget the keys inside. You should verify your identity by a pin, which can be read by someone at home to you. Another comforting service.
Since you do not have the database on your car, it is not your responsibility to update it. By database, I mean the map and the road information database. The service provider updates it constantly and you simply use it.
It uses voice recognition so that there is no need to key in anything. There are only three or four button involved, one of which is the main OnStar button, and the other is the red emergency button.

The disadvantages that OnStar has can be listed as including:

The OnStar is currently only available to cars with such hardware installed in factory. General Motors is currently installing it for its vehicles.
As any marketer would do, the subscription has different plans. The plans range from basic safety plan, to having all features plus being able to call using the same system.
The “call” is done using a more powerful cell phone system. I can assume it may be out of coverage in some places. I am already sure, as it happened, that the operator could not send the directions data to the car. The car was out of the “extended coverage area” and so data could not be transferred. Probably there was not GPRS/Edge service in that area.
Privacy is already a great concern. Nobody wants to be tracked and spied on using their own vehicle, by a subscription fee they themselves pay. I also find it really uncomfortable to have a microphone equipped remotely activated system around myself all the time.
Insurance companies can use the data gathered by the car to avoid paying insurance expenses.

Links:

OnStar on Wikipedia
OnStar in HowStuffworks.com
Court to FBI: No spying on in-car computers
- The FBI and other police agencies may not eavesdrop on conversations inside automobiles equipped with OnStar or similar dashboard computing systems, a federal appeals court ruled.