DAS Project Portal

A DAS project is often a collaboration of multiple parties - site surveyors, designers and engineers, integrator  cable  and equipment vendors, client project managers, end-user project stake holders, etc.
A common work-space can help this kind of collaborative environment tremendously. A place to post updates, schedules, upload common documents, project notes, pictures, issues, etc.
We created DAS project portal with this goal.

It takes less than a minute to start a username and password protected simple project portal.
Well organized, easy to navigate.
Available from field or office, laptop as well as smart phones.
One of the cool features is the sharing feature. Easy to share between multiple users at multiple organization(s). You can share the whole project (with all the text, pictures, files) really easily by sending a e-mail notification. And if you just want to share a single file instead of the whole project portal, it's just as easy.  

After the break check out a few snapshots of one such project portal.

Power Plant 101 for DAS

Not all of us in DAS have to deal with power plants, but having some basic knowledge does not hurt. That's the purpose of this post - a basic, high level summary of how a power plant for DAS or BTS head-end works.

Google adds Indoor Maps

Over 10,000 floor plans of selected locations are available in Google Maps across 9 different countries such as Belgium, Canada, Denmark, France, Japan, the United Kingdom, the U.S., Sweden, and Switzerland. Check out indoor maps availability on your desktop. "Simply zoom in on a building on Google Maps and you’ll automatically see a detailed floor plan with helpful labels for gates at the airport, stores within the mall, departments within a retail shop, as well as ATMs, restrooms and more." (Google Post)

How accurate are these? Let's just say I could not find Chili's on this floor plan :)

You can add your floor plans to Google Maps here. As DAS engineers and project managers we get to see a lot of floor plans daily. However, not sure what kind of privacy clause will we fall under. So I don't see myself uploading any floor plans any time soon. Despite the limited number of floor plans and upload issues I don't need to explain why this is a good news for DAS designers and engineers.

Memoto Lifelogging Camera

Memoto camera is a tiny, automatic wearable camera that gives you a searchable and share-able photographic memory. You will find the features very interesting and exciting. Still in funding stage, you can check out the Kickstarter page.

So how can it add any value in DAS?

Mobile App Wishlist: Signal on floor plan

Android Tablet

I want an app that allows me to capture signal strength and signal quality data right on the floor plan during my site survey. Yes, there are Drive Test Wireless Network Optimization Tool out there (E6474A from JDSU for example) that can do what I am wishing for and lot more (and we definitely have need for them); but I am not looking for a Mercedes to go for shopping when a Toyota Corolla will do. With Android app and tablet (not iPAD), I think this is relatively "easily" possible. Let me qualify "easily". I am not an Android programmer, but searching through the Android Developer's Library I see quite a few ready-made, albiet basic commands (Public Constructors and Methods in Android jargon) that can be integrated in Android apps. These commands cover CDMA, GSM, UMTS, etc. It's not a comprehensive list, and neither are all the parametrs in DAS are available in this library. But there are enough to create a floor plan with signal readings (see a list of commands after the break).

A letter to the Team

Here is an email went out to a team within our company. Posting it for future reference:

Gentlemen,
On 11/6/12, you accepted this mission of submitting 39 COPs by 11/12/12, 7 more ISD COPs by 11/9/12, and 6-7 more COPs by 11/12/12. Please ration your time well, and plan ahead, and work as a team to get this completed. If you have to work through the weekend, prepare yourself to do that.

What does working as a team mean?

1. If your team does not reach the goal, you did NOT reach it. It does not matter what you did.
2. Does that mean you will be penalized for working harder and pulling more weight? No. Not if you hold your team accountable. All work is divided. If you are done with your part, help your team-mate - but at the same time hold him accountable (i.e., "You were supposed to do this....")
3. Be a leader and provide leadership. Title does not make a leader. What this means is plan by looking at the goal; if you have to change plans, talk to the team, replan, regroup. If your team does not listen to you, that means either the plan was bad, or you were not convincing enough. 
4. Respect each other. This is constant in any effort - if I have to explain this, I need to talk to your mother.

Inventory List generated by DAS system

Did you know your DAS can probably generate an inventory list of what is on the system - serial numbers, soft labels, etc.?
This is very valuable. Most of them are downloadable as CSV (comma-separated values) file - this is essentially an Excel file. By changing some formats it is easy to make it visually appealing, and a valuable tool. Customer often asks for serial numbers of RF devices to be included in the close-out package. Instead of going to every remote devices and taking down the serial numbers, this is an easy and quick way to collect those information.

Following are some samples from SOLiD and MobileAccess DAS. Format of the CSV files were updated for better visualization.

DAS Head-end Board with Visual System Overview (VSO)

I recently went to a Neutral Host DAS head-end which we installed a few months ago. It took me a at least 10 minutes to figure out how all the head-end devices were connected. That was too long, considering the fact I engineered the head-end and did principal share of the commissioning and integration. If it took me 10 minutes, it will take others a lot longer.

In order to avoid similar situation in future, we updated the labeling (basically, added a lot more labels), and added a Visual System Overview on the wall. Lets call it VSO (since we are technical people, how can we not come up with another geeky term?!!)

Impact of in-building renovation on existing DAS, and how to approach it

In recent months we did maintenance work on existing DAS at different venues - both before and after renovations (upgrading interior, adding walls, or various other activities). Depending on the extent of these renovations, if not properly coordinated, it is quite possible to fall into different kind of service impacting problems. We were asked by one of our clients to put together a generic process to address issues related to renovation at any generic site where there is currently a DAS.

Overall this process is simple:

Real purpose of a DAS

The real purpose of DAS is to provide joy to the customer while she is on her phone.

Well... we cannot guarantee joy of any conversation, but our goal is to make sure the phone (i.e.,  the network supporting the phone), does not become a source of consternation. No choppy sound! No static in the line! No long call set up time! You don't have to raise one leg and tilt 45 degree on your left side to get a good connection. We don't want you to keep uttering that famous phrase like a broken record, "Can you hear me?"

We want the phone to become invisible during your conversation - so that you can just focus on the latest Justin Bieber gossip. And if you do decide to make that fake static sound to avoid talking to your boss or mother-in-law; we just want you to know... we had nothing to do with that. When you hang up the phone, we want you to think about the conversation you just had, and not start cursing the phone.

We don't need you to worry about all those KPI parameters - RSSI, RSCP, Ec/Io, link budget, propagation plots, Uplink-Downlink mumbo jumbo! We got that!

We just want you to have a great calling experience, that's what the phone was made for anyway!

Indoor geo-tagging application for DAS: recent progress

Traditionally, drive test data is tagged with latitude and longitude data. The end result is nice visual of RF signal parameters on a heat-map on Google Earth for example.

When it comes to indoor RF data collection, technology is little primitive from the perspective geo-tagging. Regardless of the equipment you are using, whether a JDSU (Drive Test E6474A Wireless Network Optimization Software), or Commscope's Invex walk test unit, when you are indoor you will have to click on the floor plan every few seconds to show where you are so that the data can be plotted accordingly. This is not automated geo-tagging.

Indoor navigation technology, however, is evolving rapidly. I can see indoor geo-tagging coming to a RF software sooner than later. Indoor navigation technologies such as Smartsense or IndoorAtlas are not just on drawing board or conceptual phase, designers actually have working models. So it's just a matter of time when we will see these incorporated in different DAS tools.

Trend: lightRadio for DAS

Back in March I had a blog post about Alcatel Lucent's awesome lightRadio technology. This is the base station that you can hold in your palm, and it's as big as a Rubik's Cube. Well, it looks like Sprint will use the lightRadio mini base stations to augment coverage and provide added capacity. Sprint's initial focus will be to use it indoors, for places with high traffic such as entertainment venues, campuses or transportation hubs. Will lightRadio be used as a RF source for DAS? There are no details, but I am sure it will be - just a matter of time. Read more.

Using small cell units to serve DAS: few thoughts...

:: Abu Sayeed
From all indications in the industry, it appears that small cell will be the wave of DAS future. In the past 6 months, we worked on over 30 small cell projects to augment coverage in enterprise in-building environment. Most of the coverage areas were below 100,000 sq. ft. In all cases these small cells were used as RF source to serve passive coax based DAS. We have designed a few fiber based DAS where small cell units are the RF Source. In September, we found out about 5 fiber based DAS network nationwide where small cells have been successfully used. We have so far designed 2 fiber DAS with small cells, and expecting to deploy within next 60-90 days.

Small cell, by design, usually has limited capacity (at least as of today). For an example, AIRAVE Pro Connect (a.k.a. eFemto) supports 29 active 1x voice calls AND 32 active EVDO Rev A sessions.  A Fiber DAS, on the other hand, is usually designed for a large coverage area where we expect to have higher traffic. This presents a sort of design objective dilemma and contradiction. As a result, when we are specifying a small cell to work as a RF Source for a fiber DAS, we have to analyze the traffic projection. It is possible to break up the DAS head-end in multiple sectors and have each sector to be served by one small cell unit. Make sure that small cell you will use can actually do hand-off with other small cells. Few other factors you may have to keep in mind while designing a DAS with small cell:

Those numbers on cable...

On a recent troubleshooting event, we found that the cables from the public safety and another service provider's antennas were crossed. This created some interesting problems. 


Once we suspected the crossed cable (thanks to Kevin Wysocki), tracing the cables from the roof-top antennas to the head-end equipment became the main challenge - in this particular case, cables from roof-top antennas to lightning protector were all LMR 400, and then from the lightning protector to the equipment were all 1/2" RFS cable. The fact that most of these cables are hidden above the ceiling tiles didn't help either. This is when the numbers printed on the cable comes handy.

Single Point of Failure

I recently (inadvertantly) rebooted a DAS in a courthouse by leaning on the wall. Talk about Hall of Shame...

I was troubleshooting the public safety part of an existing multi-carrier DAS, sitting on the floor, hooked up to the DAS head-end.  After a while got tired, and leaned back on the wall. There was a single plug going into the wall outlet which was connected to 2 UPS units, the whole head-end was connected to these 2 UPS units - basically, this DAS had a single point of failure. While I leaned back, I guess, I wiggled the plug and the power connection went out. Although UPS took over, but the latency in the UPS made the DAS reboot (this reboot shoud not have happened, but it did!). 

Besides the fact that I may be few fries short of a happy meal, I learned a few things:

1. Do NOT to use a plug with its stem sticking out. Touching the stem (especially accidentally) may cause problem.

DAS Flower: an interesting way to understand DAS platform

If you are new to DAS, here is an easy way to understand DAS platforms by solving a very simple puzzle. Based on 3 simple rules below you will have to figure out what will be the connection type in picture 1 between the blue ball (Antenna) and the square box (media converter)?

3 simple rules:

1. RF travels on coaxial cable. Antenna can only receive RF signal.
2. Loss of signal is high in a coaxial cable (signal loss is 50% every 100 ft for a typical ½” cable)
3. Signal loss in fiber is minimal even on a long run (such as over 1000 ft) 

Controlling Uplink ALC for a BDA

Often times, if an indoor BDA (Bi Directional Amplifier) system’s uplink is not properly optimized, it can create a lot of problem at the cell site due to uplink noise issues or excess power. BDAs often try to keep the Uplink (UL) and Downlink (DL) balanced, by keeping same gain in both directions or by a few dB offset. In this post, I am proposing to keep the BDA on its ALC (Automatic Level Control) feature and  limit the UL ALC to a level which can be calculated and then adjusted based on real situations. This discussion is for a CDMA system where power management is an important issue.

Assume that you want your uplink signal to hit the donor (i.e., Cell Site) BTS at -85 dB. Then for the above diagram, a basic link budget becomes,

ALCUL – Indoor side cable & other losses + Donor Antenna Gain – Free Space Path Loss – 
Clutter Loss – Fade Margin + Gain in Cell Site Antenna – Cell Site side cable & other losses = -85

Info-graphics: service affecting components in a DAS

Impact of service diminishes as you move downstream from head-end on a DAS. Need for redundancy, therefore, increases in the opposite direction.

System Map: how can it reduce troubleshooting time?

Close-out package has a lot of benefits. But it should be built around one principal premise:
How much time can it cut down during troubleshooting?

Finding out the source of the problem is a big deal during DAS troubleshooting - especially if you have a short Service Level Agreement (SLA) to resolve issues with a tough customer. Most of the DAS elements being hidden above the ceiling tile, and spread out through a building does not make life easy. A System Map can help... actually quite a bit.

System Map is essentially a spreadsheet (i.e., hardware summary) that allows a technician to quickly trace DAS elements from head-end all the way to floor level where the antennas are installed.

Designing DAS in Pilot Pollution Environment

For CDMA network, an indoor area with Pilot Pollution usually means it's an area with high signal strength, but low signal quality. This is a common phenomenon in high rise buildings in Houston (Houston, we have a problem!)

In CDMA network RSSI (Received Signal Strength Indicator) at a point is the total CDMA power received. So if at any point you are getting a RSSI of -65 dBm on a Sprint phone, that RSSI is the sum of RF Power received at that point point from all the Sprint base stations your handset can see or sniff.

Ec/Io on the other hand is an indicator of signal quality. Ec/Io at any point for a particular server (or base station) is the contribution of power from that base station divided by combined received power at that point from all base stations.

0 + 0 = 3

One of my favorite questions to ask to a new DAS engineer during interview is what is 0 dBm + 0 dBm. Say what? Answer is 3 dBm. And here's how:

0 dBm = 1 milliwatt

So 0 dBm + 0 dBm = 1 milliwatt + 1 milliwatt = 2 milliwatt

2 milliwatt = 10* Log(2) = 3 dBm

Therefore, 0 dBm + 0 dBm = 3 dBm.

Use of Info-graphics for DAS Project Management

I often get a "say-what?" look from a group of people when they come from a diverse background. While working on a healthcare DAS project, I had to give bi-weekly status update to the project stakeholders on the client side who came from diverse background - from IT, to facilities management, nursing department, infectious control, and even doctors. Talking about a DAS project can become little tricky in these situations. After a few of the bumpy sessions, I found that status update through infographics can be very effective.

Infographics is a fancy name for presenting your data visually. If you look around on the web though, infographics is mainly focused on being visually exciting and stimulating; and I don't blame the infographer, because just presenting table of data can be little boring. However, when I am using the graphics, I try to make sure that the background graphics adds value to the update I am presenting. So for example below, you can see how the major elements of the system is connected. Audience is also getting the updates on the different elements of the system. This can be fun, and presentation can be little more interesting than just presenting drab data. Audience from different background can have a better understanding of the system and how it's connected together. I also don't like to use a lot of slides when I am presenting to my clients. If a few slides are getting the point across then I am all for that.

By the way, I used Microsoft Excel and Paint for this presentation. Approximate time to put together the graphics was 20 minutes. Once I have the base graphics prepared status update boxes take just a few minutes to update.

Blue and White Coax for MIMO

Depending on the type of DAS platform (i.e., SOLiD, Andrew, MobileAccess) you are deploying, if it's a MIMO DAS you may have to pull parallel cable. For those who are not familiar with MIMO deployment, you will have to pull two sets of coaxial cable, splitters/couplers to a pair of antennas at the same location only 4-6 ft apart. In the field, this may become little complicated, because you don't want the parallel cables to get crossed. Installers usually mark the tip of the cables before pulling so that they can differentiate the cable sets.

One idea might be using cables of different color. So for example, you can pull a set of blue coax, and white coax as parallel network. I am strictly looking at it from the perspective of reducing confusion; however, logistically this may become a little complex - especially if the two colors of coax are produced by different manufacturers, etc.  

Cut me a slack...

During the DAS deployment phase, it's not unusual for cable pullers to leave some slack at the points where connectors will be installed. They do that with the thinking that having a little slack is much, much better than coming short on cable run at the point of, say, splitters or couplers. I had been in a project recently where the crew chief picked up a few crew from the local Union Hall to pull cables, and to make things simple and straightforward asked them to leave 5 ft slack at every connector point. This ended up costing us 15 ft of wasted cable per 2-way splitter or directional coupler (3 ports, 5 ft per port, a total of 15 ft). Waste doubled because this was a MIMO system. This waste is in addition to the waste we usually get from reaching the end of the spool. So when the crew chief asked for additional cable, we started suspecting the scale of the design first. We got more puzzled when we found that design was done according to the right scale. It took us almost over a week before we could figure out the principal cause.

A slackin' Situation

For this particular MIMO project, we had close to 376 antennas, 33 remotes, and 306 splitters/couplers. Just for the 5 ft slack at each connection point, the waste came out to be about 6,635 ft. From materials perspective, best thing to do is to connectorize as you go. In that case though, you may have to have crew who pulls cable and also knows how to put connectors on.

Walking-Coffin

We often use low tech thingy-ma-jiggy to build hi-tech network. One such device is - as the builder Jeremy Tesson fondly calls it - Walking-Coffin. Walking-Coffin may look like a transport vehicle for Fred Flintstone, but this was used to pull 2 sets of coax simultaneously for a neutral host MIMO DAS, where 2 parallel coax were going to 2 different antennas at a single location.

I also liked the way Jeremy accesorized the walking-coffin - a front end basket to carry around hardware and light tools, a hook to hang a dust pan. Cool!

lightRadio: a new promise for DAS

Base Station on the palm of your hand

Here is a paradigm shifting technology from Alcatel-Lucent (ALU)… lightRadio. A Base Station that fits in the palm of your hand. It’s generating bold, disruptive titles such as: “The tiny cube that could save wireless”, “lightRadio shoves a base station in a box”, “End of Mobile Towers?” – and they are all legitimate claims or predictions.
Even bigger news is that is not a concept anymore.  Telefonica, whose customers are in 25 countries across Europe and Latin America, announced the first live test of the 4G network over lightRadio, and the cube was supporting 1,000 users at the last Mobile World Congress of 2012 in Barcelona in February.

I am illustrating some basic configuration block diagram of lightRadio cube based on the information provided by ALU.

QR Code in DAS: is it feasible?

QR Code is an interesting new technology. Invented in Japan, QR is short for Quick Response. They can be read quickly by a smart phone by using QR reading apps. They can store more information than a standard bar code; such as URL links, Latitude and Longitude, text (upto 250 characters) etc. Another advantage over bar code is that you won't need a separate hand-held scanner, by using QR reading apps on your smart phone you will be able to read them.

Here is an example...

This is a QR Code for a text phrase, "Relax! It's On Air". I used a free QR generator at Kaywa. For reading this QR I use a free Android app "Qr Barcode Scanner" on my Smasung Galaxy S2. There are other free QR Generators as well as readers available. [To learn more about this technology, you can read Marc Lyne's article or check out the USA Today article, "What's a QR code and why should you care?".]

Can we use QR code for DAS industry?
We are exploring a few options in a current DAS project in a large healthcare campus expected to be completed in a month.