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.