LTE Femtocell SON
      III 99
Outline



Interference Avoidance Mechanism.

Other issues
Motivation


Femtocell SON not only reduce OPEX
and CAPEX but also improve user
experiences.

It’s a new approach
Interference
Avoidance Mechanism

Dead-zone effect mitigation

  by linear-time negotiation

  in Hybrid access mode
pr ov id e su ff ic ie n
                                                                                              tra...
Dead-zone effect
    mitigation


Assume time of all the Femtocell is
sync. by the covered Macrocell
Dead-zone effect
mitigation (cont.)
Macro-cell maintain a limited-size
LRU-proximity cache, ex. n: (number
of FAPs * K) in...
Cache Table                     (prototype)

     status          RB freq RB freq
id    bit
              tick            ...
Dead-zone effect
mitigation (cont.)
Using Distributed RB-allocation
algorithms

Negotiation between FAP and the
Macrocell
...
case I

Femtocell
has a new
   call
case I

Femtocell
has a new
   call
// Periodically check
      for each RB in Cache Table{
         ((RB is in use)? tick++: tick/=2);
         if(tick<1) {
...
// Periodically check
          for each RB in Cache Table{
             ((RB is in use)? tick++: tick/=2);
             i...
case II

Macrocell
has a new
   call
case II

Macrocell
has a new
   call
// Periodically check
     for each RB in Cache Table{
        ((RB is in use)? tick++: tick/=2);
        if(tick<=0) {
  ...
// Periodically check
     for each RB in Cache Table{
        ((RB is in use)? tick++: tick/=2);
        if(tick<=0) {
  ...
// Periodically check
          for each RB in Cache Table{
             ((RB is in use)? tick++: tick/=2);
             i...
Dead-zone effect
mitigation (cont.)
Centralize Interference Avoidance

Time Complexity per request : O(n)

   Check Cache ...
Hybrid Access mode


Prioritized requests are preemptive.

  To ensure the QoS of CSG list
  user.
SON use cases
                                                                               Energy         Load        HO...
SON use cases
                                                                               Energy         Load        HO...
Energy Savings
switching cells on/off

   Context:                    FAP,                       FAP


DL Power

   adapti...
Load Balancing

cell reselection

   cache scheme for speed up the macro-tier to femto-
   tier switching

       A Cache ...
Load Balancing
     (Cont.)

cell reselection

   adjusting parameters of different characteristic
   RF environments

   ...
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  1. 1. LTE Femtocell SON III 99
  2. 2. Outline Interference Avoidance Mechanism. Other issues
  3. 3. Motivation Femtocell SON not only reduce OPEX and CAPEX but also improve user experiences. It’s a new approach
  4. 4. Interference Avoidance Mechanism Dead-zone effect mitigation by linear-time negotiation in Hybrid access mode
  5. 5. pr ov id e su ff ic ie n traffic bottleneck. works provide lat current backhaul Scenario A: forward link provide delay res (BS to mobile) po se s a se ri ou s c Macrocell transmits to cell edge the wireline back user in femtocell dead zone pany or in a tight cellular operator. A no th er is su e Scenario A: reverse link (mobile to BS) occurs when the to deliver Wi-Fi reveal that when cells experienced ev en lo w -b an dw especially impor Femtocell transmits to vo ic e co ve ra ge i home user and creates for femtocells. dead zone for macro user Nearby macrocell user PHYSICAL AN cro BS and transmits with high power to ma ll user creates dead zone for femtoce V For voice users femtocell ne tworks. ei th er al lo ca te I Figure 2. Dead zones in CDMA Dead zone macrocell and fe sig- tie r in te rf er en c will require synchronization to align received femtocell users erence and nals to minimize multi-access interf to maximize are Synchronization ensure a tolerable carrier offset. can hand th e sc ar ce av a is also required so that macrocell users ea se of de pl oy w hi ch is m ad e of f to a fe m to ce ll or vi ce ve rs a,
  6. 6. Dead-zone effect mitigation Assume time of all the Femtocell is sync. by the covered Macrocell
  7. 7. Dead-zone effect mitigation (cont.) Macro-cell maintain a limited-size LRU-proximity cache, ex. n: (number of FAPs * K) in the Macro-cell. Each slot contains status-bit, tick, and available resource block information
  8. 8. Cache Table (prototype) status RB freq RB freq id bit tick PCI QCI - start end 1 1 30 0xff00 0xff7f 22 3 - 2 0 0 0xff80 0Xffff 23 7 - - - - - - - - - - - - - - - - -
  9. 9. Dead-zone effect mitigation (cont.) Using Distributed RB-allocation algorithms Negotiation between FAP and the Macrocell Macrocell initialize with a limit size RB Pool
  10. 10. case I Femtocell has a new call
  11. 11. case I Femtocell has a new call
  12. 12. // Periodically check for each RB in Cache Table{ ((RB is in use)? tick++: tick/=2); if(tick<1) { bit = 0; if(!Pool_is_full) Push(RB); } } Macrocell Femtocell By Distributed RB Alloc. Algo. Allocate Resource Block if (!found || found && bit=0) Case I: int releaseRB(int REQ_QCI){ Accept, Cache RB, Set bit = 1 int goal= (9-REQ_QCI); int cnt=0; //!RB: no suitable RB if (found && bit=1) while(!RB && cnt<goal){ for each RB in Cache Table{ Case II: if(QCI==(9-cnt)) { Allocate available RBs from the Pool Push(RB); AdjustHandOffParam(RB); and retrieve another available RB } } to instead later cnt++; if(!available RB) _ALLOC_OK = } (cnt<goal? return 0: return 1); releaseRB(int REQ_QCI); }
  13. 13. // Periodically check for each RB in Cache Table{ ((RB is in use)? tick++: tick/=2); if(tick<1) { bit = 0; if(!Pool_is_full) Push(RB); } } Macrocell Femtocell By Distributed RB Alloc. Algo. Check Allocate Resource Block Cache Table if (!found || found && bit=0) Case I: int releaseRB(int REQ_QCI){ Accept, Cache RB, Set bit = 1 int goal= (9-REQ_QCI); int cnt=0; //!RB: no suitable RB if (found && bit=1) while(!RB && cnt<goal){ for each RB in Cache Table{ Case II: if(QCI==(9-cnt)) { Allocate available RBs from the Pool Push(RB); AdjustHandOffParam(RB); and retrieve another available RB } } to instead later cnt++; if(!available RB) _ALLOC_OK = } (cnt<goal? return 0: return 1); releaseRB(int REQ_QCI); }
  14. 14. case II Macrocell has a new call
  15. 15. case II Macrocell has a new call
  16. 16. // Periodically check for each RB in Cache Table{ ((RB is in use)? tick++: tick/=2); if(tick<=0) { bit = 0; if(!Pool_is_full) Push(RB)); } } Macrocell Femtocell Case I: if (!found || found && bit=0) Accept, Cache RB, Set bit = 1 Case II: if (found && bit=1) Allocate available RBs from the Pool, another available RB will be recruited later. Then, cache the new RB and set bit = 1
  17. 17. // Periodically check for each RB in Cache Table{ ((RB is in use)? tick++: tick/=2); if(tick<=0) { bit = 0; if(!Pool_is_full) Push(RB)); } } Macrocell Femtocell Case I: if (!found || found && bit=0) Accept, Cache RB, Set bit = 1 Case II: if (found && bit=1) Allocate available RBs from the Pool, another available RB will be recruited later. Then, cache the new RB and set bit = 1
  18. 18. // Periodically check for each RB in Cache Table{ ((RB is in use)? tick++: tick/=2); if(tick<=0) { bit = 0; if(!Pool_is_full) Push(RB)); } } Macrocell Femtocell Check Cache Table Case I: if (!found || found && bit=0) Accept, Cache RB, Set bit = 1 Case II: if (found && bit=1) Allocate available RBs from the Pool, another available RB will be recruited later. Then, cache the new RB and set bit = 1
  19. 19. Dead-zone effect mitigation (cont.) Centralize Interference Avoidance Time Complexity per request : O(n) Check Cache Table: O(n) btw, Periodically update: O(n) Space Complexity - O(n)= O(C+P) Cache Table Size: O(C) Pool Size: O(P)
  20. 20. Hybrid Access mode Prioritized requests are preemptive. To ensure the QoS of CSG list user.
  21. 21. SON use cases Energy Load HO Relay & Coverage eNB Coverage & ANR; balancing optim. repeater mgmt hole mgmt insertion capacity opt. savings Phy cell ID ICIC Switching HO MIMO RB DL Tx Antenna Neighbor parameter configuration Power tilt cells on/off lists assignment Potential optimization parameters meters Figure 8: SON use cases and potential target para What parameters This is a meaningful insight because it minimizes the risk of jeopardizing Other issues need optimizing? benefits and triggering conflicting or adverse effects such as oscillations One of the key issues is pinpointing when tuning several parameters at the parameters to be targeted for a time. optimization. One of the key enablers for robust and
  22. 22. SON use cases Energy Load HO Relay & Coverage eNB Coverage & ANR; balancing optim. repeater mgmt hole mgmt insertion capacity opt. savings Phy cell ID ICIC Switching HO MIMO RB DL Tx Antenna Neighbor parameter configuration Power tilt cells on/off lists assignment Potential optimization parameters meters Figure 8: SON use cases and potential target para What parameters This is a meaningful insight because it minimizes the risk of jeopardizing Other issues need optimizing? benefits and triggering conflicting or adverse effects such as oscillations One of the key issues is pinpointing when tuning several parameters at the parameters to be targeted for a time. optimization. One of the key enablers for robust and
  23. 23. Energy Savings switching cells on/off Context: FAP, FAP DL Power adaptive sleep interval (wake mode v.s. sleep mode) An Adaptive Energy Saving Mechanism in the Wireless Packet Access Network.pdf discontinuous reception mode (RRC_IDLE states v.s. RRC_CONNECTED states) DRX Mechanism for Power Saving in LTE.pdf
  24. 24. Load Balancing cell reselection cache scheme for speed up the macro-tier to femto- tier switching A Cache Scheme for Femtocell Reselection.pdf adjusting the cell reselection criteria based on the access probability in the serving cell and neighboring cells UEs shall reselect a cell with a higher access probability Access Probability Aware Cell Reselection for Load Balancing.pdf
  25. 25. Load Balancing (Cont.) cell reselection adjusting parameters of different characteristic RF environments Cell Reselection Parameter Optimization in UMTS.pdf
  26. 26. Thanks for your listening

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