Round Up 2013

Lets recap what we have covered in the year 2013. This year we took a diversion initially from the cellular standards and moved to Wi-Fi , WiMAX etc. I also covered the Fi-Wi networks. Then we looked into the data challenge from the network perspective and device perspective.We also understood some concepts related to the In building Solutions , DAS etc. Then we switched to the hardware part. Antennas basics/ recent developments and OTA testing..I received a request for covering the LTE signalling procedures so we went into that. We ended this year with learning Interference.

I hope you a had a great 2013. Happy Holidays!

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Follow Up : Antennas

Here is some more information about the latest development in antennas. The main advantage of using the smart antennas is efficiency in terms of cost and performance. The concept of smart antennas took shape while the OEM's were busy making the devices thinner and 3GPP was implementing MIMO and other technologies for better performance. 

The push from both these ends helped the growth of smart antennas. The smaller sizes and higher capacity was achieved using these antennas.

Lets discuss some details about the DOA estimation , beamforming and a little about MIMO (as we have already covered this in the LTE Follow-up)


DOA Estimation : DOA stands for Direction of Arrival. There are antennas that can estimate the direction of arrival of the signal and act accordingly, isn't it smart! We get the advantages of the directional antennas without the restrictions that come with it. There is a sensor array that has multiple sensors and it determines the direction of the radiowave propagation.

Beamforming : Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception! Beamforming is done using conventional methods or adaptive methods.  Adaptive beamforming provides the flexibility of working across different situations.

MIMO : Multiple Input Multiple Output techniques are widely used in LTE and advanced standards.It supports higher data rates and provides higher resistance against multipath and channel fading. I don't want to repeat what we already discussed in LTE : Follow up here. There is one advanced concept here, MuMIMO - Multi user MIMO. In this case multiple user devices can transmit simultaneously on the same resource block.

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Antennas

Now that we have covered cellular and other wireless standards. Lets move to the hardware side of it.. We will be discussing the antennas. 

Lets start with the basic definition of what an antenna is.. "An antenna is a transducer that converts the electrical power into radio waves or vice versa.." This Wikipedia definition says it all..I hope it answers the question of "How exactly does the transmission happen?"...Most importantly I do not claim that this post can be used as a comprehensive guide for antennas. I am trying to catch a glimpse of the wide subject.

In this post , lets understand the following details about antennas.

1. Fundamentals
2. Types
3. Antenna Design Concepts


1. Fundamentals 

The antenna has certain characteristics.. Here are some important parameters related to antennas.

• Frequency : Any antenna is designed for a range of frequencies. 
• Reciprocity : For any antenna, the characteristics when it sending the data and receving the data remain same. This is a fundamental property of any antenna.
• Gain : Antenna gain is a measure of how the antenna focuses available power away from a spherical wavefront to a limited number of directions
• Polarization : It is the orientation of the Electric field. An antenna can have linear/circular or elliptical polarization.
• Densitization/Desense  : Degradation of the sensitivity of an antenna due to noise.
• Effective Isotropic Sensitivity : Sensitivity of antenna in a single direction.
• Effective Isotropic Radiated Power : It is calculated as (Power - Loss + Gain)
• Radiation Patterns : This is a relative pattern in 3D. This depicts the relative strength of radiated field in various directions from antenna at const distance.

2. Types of Antennas : 

The antennas can be categorized depending on the frequency ranges they support , the directional properties or application.

a. Depending upon Directional properties

• Omni directional : These antennas transmit in all directions. (Its not isotropic!!)
• Semi directional : These have a broad sense of direction and accordingly the radiation pattern.
• Highly directional : This antennas are most widely used antennas , they propagate in a very specific direction.  Examples include Yagi antenna , Dish antenna , Patch antenna etc

b. Depending on the Application

There are antennas used for point to point or point to multi point communication.

3. Antenna Design Concepts

Here is the basic list of parameters one should keep in mind while designing/selecting antennas.

• Frequency Requirements
• Conductor Types
• Dimensions
• Placement 
• Regulations

In the next post , lets look at the Smart Antennas. Propagation Engineering and Practical Antenna Handbook are "MUST" reads on this topic.

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IBS/DAS continued..

This being holiday season, I am going to keep the post simple and short.
In this post I intend to cover the indoor radio planning procedure.
The entire process can be divided into several stages.

1. Getting accurate information.  It is essential to get accurate information about the type and number of users. Floor-plans, architectural details of the site , existing systems etc.

2. The Site survey : Some people say that it is better to do a site survey even before coming up with the preliminary design, as far as I am concerned , it would be better to come up with the preliminary design and then go ahead with the site survey so that it would be easier to relate the tool output and the data collected on the field.

3. The design will be modified after the first site visit. It is beneficial to be as accurate as possible so it would be easier to optimize/tune the system once it is installed.


4. Optimize the system : It would be impressive to meet all the required KPIs on the first go and if one can not achieve that, there is always scope for optimization.

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IBS/DAS

As I am planning to dig deeper into IBS/DAS this month, I came across some interesting articles and books. I think the "Indoor Radio Planning" book is one of the most extensively written book I have ever come across about the subject.
It is a must read (if you belong to my category , 'the ones with little experience!! :('  )

First and the most basic question would be , why would operators invest for in-building coverage? Why not use the coverage from outdoor Macro sites ? Why pay so much ? To answer this question in simple words , they are getting a boost in their traffic and hence revenue. Lets consider an example of shopping mall , ( being a frequent-shopper  I can completely relate to it), If I have good coverage inside the mall, I tend to get the pictures of the dress I am trying on and ask my friend for her opinion if I am confused. (See there is some boost in the traffic). Studies have shown an instant boost in traffic upto 120-140%. In the long run investing in the "in-building coverage" is going to be financially beneficial for operators.

Now that we are clear about why we are doing what we are doing. Lets move to the Basics. 
There is one most important parameter that one needs to understand/consider while designing an indoor system. "ISOLATION" !! Proper isolation has to be maintained between in-building and macro systems.  That means we want our inbuilding sector to be dominant inside the building and there should be minimum spillage from the sector outside of the building. Very simple concept to understand but can give you some tough time depending upon the building architecture. Planning the antennas is a different thing and installing those at the exact same location is another big task.

The next important aspect of any DAS is the components. Lets look at this simple diagram explaining the DAS architecture. This picture is taken from the same book.

As the diagram explains, there are different components of the system. Each has certain specifications, compatibility issues etc. Fortunately the tool takes care of the compatibility and the losses. Otherwise after selecting the CAT cable, one would have to look at the frequency and then decide on the length , get the loss etc. Tools also help us by calculating the power 

In the next post of the month , I will be covering the indoor design procedure.

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Inside the building : Continued..

4. Tools : Well, I am sure everyone is aware of iBwave and their certifications. If not, please go to http://www.ibwave.com/..This tool is now almost used as a standard. I like the details they have covered while designing the tool. Many operators do have specific requirements for the design (then I realized the importance of this certification)..

More inputs like, photos from site surveys, floorplans, intended area of coverage, material of walls/cabins, type of floor, location of pillars play a very important role!! It might not seem necessary to go to such minute details but it indeed is. (One single prediction plot after defining walls will show a big big difference)

5. Optimization : Well a well designed network can be easy to optimize but that wont be the case always. A perfect design also will need tweaks. Optimization includes making intra and inter frequency handoff work, making the sector boundaries visible, having good uplink and downlink performance, not having any coverage hole, not having multiple sectors equally dominant at the same location. There are different KPIs to be covered in this phase like, call drops, attachments rates, handoffs between sectors, CSFBs . These might need specific tests. These tests are sometimes operator specific. 

6. Noise/Traffic/Link Budget : Link budget part is generally easy to generate. The tool helps you in that. Noise can be tricky to handle as PIM can trouble you big time!! Traffic (and those erlang charts) is an important consideration while designing and optimizing the system

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Getting Inside the building

Well I thought I will be able to write about VoLTE and Network deployment but I figured out that I am still not ready for that. It is going to take some more reading and understanding from my side. So I decided to go ahead and get inside the building!!
Yes , this month the focus is going to be In-Building Solutions, DAS and some more cool words!! :)
Most importantly I am not an iBwave expert or IBS/DAS expert. I liked this area so I started reading and understanding more.
There are a very few (actually very very few) books available on this topic. So I am still finding out as much as I can.
Here is the list of topics I intend to cover this month.

1. Need and Importance of IBS
2. Introduction to DAS
3. Designing Indoor DAS
4. Tools
5. Optimization
6. Noise/Traffic/LinkBudget

1. Need and Importance of IBS : First and foremost, why IBS ? Before implementing any new technology or concept, the "WHY" part is essential. Is it necessary to answer questions like , profits/total number of users/kind of data traffic/current coverage due to Macro etc. Why not have macro coverage (sometimes from multiple sites), what would be my cost benefits , quality etc. Then comes the futuristic plans, is there enough scope for expansion for new services and more operators.These and lot more questions need to be carefully answered even before one starts designing any DAS system.

2. Introduction to DAS : DAS- Distributed Antenna System. What exactly is this? According to wikipedia, " is a network of spatially separated antenna nodes connected to a common source via a transport medium that provides wireless service within a geographic area or structure."  There are three types of DAS, 
 Active DAS, Passive DAS, Hybrid DAS. 

a. Active DAS : Active DAS has the ability to automatically compensate for the losses of the cables interconnecting the components in the system by using internal calibrating signals and amplifiers. It does not matter what the distance between the antenna and the base station, all antennas in an active DAS will have the same performance 


b. Passive DAS : Passive DAS in opposite to the Active system does not compensate for losses due to cables or components. Hence it is used in smaller buildings.

c. Hybrid DAS : As the name suggests, its a combination of both!!

I want to go through details of all these three types of systems, there components, power levels, Uplink/Downlink performance and more.. Lets do it next month.

3. Designing Indoor DAS : This is the most important and interesting part. I want to elaborate this section. 

The first and foremost step here is the need of installing DAS at a particular location. There are multiple factors affecting this decision. Next step would be from the financial side , the investment/returns etc.. Third step would be RF planning. Many tools are available for this (iBwave, Ekahau, Airmagnet and so on ) ..Site surveys , initial design need to be done in this phase of the project. Elevators, handoffs , spillage (isolation of DAS) also need to be considered while designing the system. Whether the system is single/multi operator also needs to be taken into account while designing. This month is just introduction to DAS, we will get into details of everything as we go forward.

I can go on , but then the post will be too long.As I said, it is just introduction , we will get into all the details soon. 

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The DEVICE side of it

In this challenging month, we discussed about the data challenge from the network side, now lets move to the device side of it.

I could not find much resources about the device side of the data challenge, so I am going to write whatever I feel are the ways out.

1. Modulation techniques : Implementing higher modulation techniques can be a solution for the increasing data demands 

2. Beamforming : Advanced beamforming techniques can also serve as a solution.

3. Smart Antennas : Antennas capable of implementing MIMO or multi user MIMO.

4. DSP : A better or improved data processing and algorithms.

Next month I am going to talk about VoLTE and Network deployment!

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This month, lets discuss about the Data challenge..Everyone is talking
(worrying) about the increasing number of connected devices, increasing data usage, mobile data offloading, hotspots etc etc..So lets discuss the mobile tsunami this month..
The solution needs to come from both sides, device as well as network side.




From the network side , to tackle the increasing number of users and higher data demands the networks people have come up with may different ideas. So here we are. There are three major solutions to tackle the increasing mobile data demands. Lets discuss them one by one.

1. Data offloading: The words are explanatory. In this case, the data is offloaded or transferred to the other possible options or existing networks. This is the reason we find "hotspots" everywhere these days. (And get happy that I'm not wasting my data). WiFi and femtocell are most popular ways for data offloading.

2. Using more spectrum: The concept of ASA (Authorized Shared Access) concept was explained in one of the Qualcomm webinars. I think it was proposed by Nokia and Qualcomm. In their words, ASA is defined as "To Enable Timely Availability and Licensed Use of Harmonized Spectrum for Mobile with Predictable Quality of Service." 
{source: http://ipsc.jrc.ec.europa.eu/fileadmin/repository/sta/corsa/docs/SDR_ASA.pdf}

Let me explain this concept in detail, In ASA , the bands which have been already assigned to defense/satellite/broadcasting etc can be shared for mobile broadband as these are not used 24*7 all days. Secondly this is licensed  so QoS can be provided.

3. Increasing Capacity: This one comes from the textbook :):)..So what all can be done to increase the capacity. The approaches of cell splitting and sectoring have already been implemented. Now macrocells, picocells and even femto cells are being planned and implemented.


Next time, Lets talk about the data challenge from the Device side.

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Bluetooth

Lets take a small deviation from cellular systems this month. Lets see WiMAX and Bluetooth.

Lets talk about the Bluetooth first !!  It operated in the unlicensed band, 2400–2480 MHz . Its basically a short distance technology. 
             The name is really interesting "BLUETOOTH". Isn't it? It's taken from a king who live in Denmark and some parts of Norway in the 10th century. He united some dissonant tribes and created a kingdom!! Bluetooth does the same. It united communication protocols and created a universally accepted protocol.
            The specs for bluetooth are 
Date rate : upto 1Mbps (Bluetooth2 is upto 2Mbps, Bluetooth3 goes upto  
                                      24Mbps)
Transmit Powers :  Class 3: 0 dBm (1 mW) 5m
                              Class 2: 4 dBm (2.5 mW) 10m 
                              Class 1: 20 dBm (100 mW) 100m
These classes are according to distance. As we can see from the distances Bluetooth is really a Wireless Personal Area Network.  

Bluetooth technology has grown at a steady pace. Bluetooth originally started with 1Mbps has reached higher data speeds and most importantly has reached lower power consumption values. Lower power has enabled bluetooth to be used in medical and fitness devices as the power falls under the safety limits. In the official release it was mentioned that the Bluetooth4 has "Ultra-low peak, average and idle mode power consumption" and also has an "Ability to run for years on standard coin-cell batteries".

In the December 2011 Issue of Vehicular Technology Magazine, IEEE there was an interesting article about coexistence of WiMAX and Bluetooth and how exactly these two technologies are present in the phone. 
Lets talk about WiMAX  next time and also the co-existence of these two.

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Fi-Wi

Its not a typo. I am not referring to Wi-Fi. I am referring to Fi-Wi! Recently I came across the research inside the Zeitgeist Laboratory. These people are working on Fiber-Wireless Broadband Access Networks. This might be the future of Networks!


According to the Zeitgeist Laboratory , "  Future broadband access networks will be bimodal, capitalizing on the respective strengths of both optical and wireless technologies and smartly merging them in order to realize future-proof Fiber-Wireless (FiWi) networks that strengthen our information society while avoiding its digital divide." They are combining both the networks hence increasing the efficiency.

There is not much information available about these networks as of now. The proposed direction of research published by the Zeitgeist Laboratory covers following points.


1. Protocol Translation : It will be done at the interface of optical and wireless segments.
2. Radio Over Fiber : RoF  
3. Architecture : The architecture reduces cost and increases flexibility
4. Reconfigurability : It is done using Wavelength Division Multiplexing PON (WDM PON)
5. Cost Efficiency : (As half the world only understands the language of MONEY!) - It is future proof as it provides pay as you grow option.
6. Autonomic Networks : Similar to SONs


More information can be found on their website.

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Wi-Fi continued..

Lets continue with the discussions about WiFi.

3 Key enabling technologies in 802.11n and 802.11ac

Why are 802.11n and 802.11ac drastically better than the previous versions/standards? As we disucssed in LTE, there are certain key enabling technologies. Lets discuss some of these here.

a. Extended channel binding
The bandwidths in ac are 80/160MHz facilitating higher data rates.

b. MIMO spatial streams
In case of 802.11ac upto 8 MIMO streams are supported.

c. Multi-user MIMO
I really find the concept of multi-user MIMO very exciting. Here in case of WiFi, multiple stations can receive and transmit data streams simultaneously.

d. Higher Modulation techniques 
Upto 256 QAM is supported in 802.11ac.

4. A peek into future

I was reading more about the future of WiFi, I came across an interesting presentation related to something called WiFi 3!! This is a technology developed by Edgewater Wireless.  Do read more on their website, I will just give a brief introduction to the same.

WiFi3 provides 50X performance improvement. They are using a multi channel (3) approach for the same. They are providing three channels on a chipset hence  giving higher throughput. They are promising better QoS and security as well.

WiGiG is an alliance for Gigabit WiFi, to support the increasing data rates, it is necessary to implement Gigabit WiFi.  The whitepaper on their website is a must read.
Here are some f the specifications they have metioned

1. Data transmission rates upto 7Gbps are supported.
2. Designed to support low power mobile devices.
3. Supports beamforming, maximizing signal strength.
4. Also supports high performance implementations like HDMI, DisplayPort, USB.

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Wi-Fi : The standard of Past, Present , Future

It is really tough to imagine life without WiFi. GSM/CDMA/LTE everything is great but when it comes to home/office internets no one can beat WiFi. There is no work around for this standard. Understanding WiFi and the related technicalities is my task for the month!! Have you ever tried downloading IEEE standards? The 802.11 comprises of 2793 pages..Lets start understanding WiFi from scratch.
Lets begin with the origin of WiFi..Well the story behind the name is not interesting as bluetooth. It all started around early 1980s and now we are talking about Gigabit speeds!! IEEE started standardization with 802.11 - 1997.  
The 802.11 -1997 or also known as 802.11 legacy mode is rarely used. The data  rates then were upto 2 Mbps. Now we are moving towards 802.11ac that theoretically enables a speed of 1Gbps. This technology has seen a huge increase in the data rates. Although the ranges have not changed much (well it depends on what does 2.5 times increase means to you!!) May be in the coming month we can talk about FiWi.Yes FiWi and not WiFi. 
WiFi networks or WLAN (Wireless Local Area Networks) are based on this IEEE 802.11 standard or what is popularly known as WiFi. 

Lets divide the WiFi discussion into these parts.
1. Architecture and terminology
2. An overview of 802.11 from a to ac.
3. 802.11 Protocol
4. Key enabling technologies in 802.11n and 802.11ac
5. A peek into future

PS : I am reading some of these topics for the first time so please do correct me if I am wrong. As I have already said, I am no expert!!

1. Architecture and terminology

WiFi has a super simple architecture, Remember the LTE networks (by the way which are simpler than the previous generations) even that network is way complex than the WiFi network. 

Yes it is this simple, it has the distribution system, access point and base station. That is it. Lets look at each of these.

A. Distribution system
This is the communication system between access points. It is the backbone network and 802.11 does not have any specifications for this.

B. Access Points 
These are the points that convert whatever 802.11 data frames to other.

C. Stations
These are our devices. Tablets/phones/laptops/desktops/ebook readers etc.

There are two different types of WiFi networks. 
Independent and Infrastructure networks. There are some definitions one should know to be more comfortable while reading the literature.
Like
Basic Service Set (BSS) : stations which communicate with each other and form a service area.
Extended service Set (ESS) : Extended service area by linking BSS.

2. An overview of 802.11 from a to ac.
Lets skip the Legacy mode for now. Detailed description can be found on IEEE website. Wikipedia also has a good page dedicated for the same.

A. 802.11 a : It was designed for 3.7Ghz and 5Ghz frequency. Uses OFDM scheme and has 52 channels. modulation upto 64QAM. Range is 120m outdoor.
Surprisingly with higher power range upto 5km can be obtained. Data rates upto 54Mbps are supported.

B. 802.11 b : Designed for 2.4 GHz, 20 MHz bandwidth, Data rates upto 11 Mbps are supported. DSSS technique was used. Outdoor range of 140m.

C. 802.11 g : Operating frequency and bandwidth and range is same as b, but supports higher data rates (upto 54Mbps). Uses OFDM and DSSS.


D. 802.11 n : Supports operating frequencies 2.4 and 5 GHz. Bandwidth can be 20 or 40 MHz and hence supported data rates are upto 72.2 or 150 Mbps. OFDM scheme is used. 4 stream MIMO can be used.

E. 802.11 ac : Designed 5GHz, supports bandwidth from 20 to 160 MHz and hence data rates upto 866.7. MIMO techniques have been used upto 8 streams. 

Exact information about timlines of these standards can be found at


http://grouper.ieee.org/groups/802/11/Reports/802.11_Timelines.htm


In the next blog, Lets discuss the remaining topics.

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Welcome 2013

Wish you all a very happy new year. Lets start the new year by looking at what's in store for us.

Here is a link to global predictions by deloitte.

http://www2.deloitte.com/global/en/pages/technology-media-and-telecommunications/articles/tmt-predictions-2013-technology-media-telecommunications-report.html

In terms of the blog posts, here is what I intend to cover

This year lets divert from the cellular standards and look at other wireless standards. We will also study more about antennas and OTA testing. Also I need to cover LTE signalling as I had left it last year. And see what else can be added.

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