I am writing this right after enjoying a rainy day (at the moment ) in Guildford, Surrey, England.

This is where I am spending my Summer of 2017. Surrey does have the climate that I would happily trade my summers here versus

spending days in the intense heat of Oklahoma and Texas.

 

 

Not only that it is in the neighborhood of London. But more importantly 5G Innovation Center ( 5GIC ) is at the University of Surrey, where I plan to spend my next 6 weeks.

 

 

 

 

5GIC is the largest research institute in Europe where hundreds of research fellows are working on the development of next generation

technology i.e., 5G everyday. In addition , it has dozens and dozens+ industrial partners , who are closely monitoring and interested in 5G

development while having a collaboration with this institute.

 

In fact, UK government granted additional money worth 16 million pounds to 5GIC for 5G trialsrecently. It proves how significant the

institute is in the eyes of industry and policy makers with respect to 5G development.

 

(Does this mean you will hear more from me about 5GIC and the things taking place here in coming weeks and months ? Probably Yes !!!

 Oh Btw, I am not being paid by 5GIC or University of Surrey to promote it in anyway. All of these opinions are based on my own research and does not reflect the interests of the above mentioned institute or its subsidies )

 

 

Now the legal stuff is out of the way. Let’s continue , as I was saying 5G is expected to get standardized by 2020 or so. Does that mean 4G

will go away. ??

 

Not at all. A lot of us are going to get our telecom career mileage by working on 4G only and related disciplines alone. While it will take a

couple of years to half a decade before 5G hits the market(s) for real.

 

Just to clarify when I say this. Yes there will be early deployments in various hand picked and selected markets for 5G, while majority

market share relies on 4G and classic technologies.

 

This brings me back to 4G and its bit rates. Two weeks ago I shared about the maximum bit rate achievable in 4G.

 

4G LTE Advanced Bit Rates

 

Today, let’s shed some light on 4G LTE Advanced and the bit rates achievable in this scenario.

 

Theoretical Throughput

 

The table A below includes the theoretical absolute maximum physical layer throughputs for a number of LTE Advanced Scenarios. It

includes

• Carrier Aggregation
• 8 x 8 MIMO

 

 

 

Table A above indicates theoretical throughput values only. These values are not possible practically.

The values in table above assume the following:

• All Resource Elements are allocated to PDSCH
• Physical Layer does not add any redundancy
• Normal Cyclic Prefix
• PDSCH is transmitted on antenna ports 7 to 10 for 4 x 4 MIMO
• PDSCH is transmitted on antenna ports 7 to 14 when using 8 x 8 MIMO

 

 

( Realistic )Maximum Expected Throughput Assumptions

When deriving maximum expected throughput , overheads generated by other physical channels and physical signals are to be taken into

the account.

 

In this case while computing the expected throughput , the following assumptions are made :

 

1. PCFICH , PDCCH and PHICH occupy either 1, 2, 3 or 4 OFDM symbols per subframe
2. cell specific reference signal is only transmitted from antenna port 0
3. No multimedia broadcast single frequency network ( MBSFN ) subframes are configured so the cell specific Reference Signal is transmitted during all subframes
4. the UE specific Reference signals occupies 24 Resource Elements within each Resource Block pair
5. In case of 4 x 4 MIMO, the channel state information ( CSI ) reference signal occupies 4 Resource Elements within each Resource Block pair , during subframes that include CSI reference signal transmissions. The CSI reference signal periodicity is assumed to be 10 msec
6. In case of 8 x 8 MIMO, the CSI reference signal occupies 8 Resource Elements within each Resource Block pair, during subframes that include CSI Reference Signal transmissions. The CSI reference signal periodicity is assumed to be 10 ms
7. Physical Broadcast Channel ( PBCH ) and Synchronisation Signals occupy a total of 564 Resource Elements per radio frame

 

 

The above assumptions lead to physical throughput presented in table B below.

 

 

 

 

The throughput values in the table B above do no account for the following:

• No Redundancy added by the Physical layer
• Do not account for overheads generated by the various protocol stack headers and retransmissions
• Do not account for overhead generated by RRC signaling

 

 

Impact of OFDMA Symbols

Table B above indicates the impact of the number of OFDMA symbols allocated to PDCCH , PCFICH and PHICH.

These physical channels can be allocated :

• 4 symbols when using 1.4 MHz channels
• 1,2 or 3 symbols when using the other channel bandwidths

 

Increase Overhead

The overhead in case of LTE advanced is increased when using antenna ports 7 to 10 for 4 x 4 MIMO.

 

Component Carriers

The throughputs shown in the Table B above increase in direct proportion to the number of Component Carriers as it is assumed each

component carrier has the same configuration.

 

However, in real practice this is not the case.

 

For example, one Component Carrier could have 2 OFDMA symbols reserved for the PCFICH, PDCCH and PHICH, while another

Component Carrier can have 3 OFDMA symbols reserved.

 

 

( References for the above discussion goes to 3GPP TR 36.912 LTE Advanced spectral efficiency and LTE in Bullets )

 

So far I have discussed throughput for the case of FDD scenarios. In the coming posts, will discuss the similar scenarios for the case of Time Division Duplexing ( TDD) .

 

Before you go , leave your comments and two cents in the comments section below.