Normal Cells

Atoll distributes traffic on the TCH service areas. The traffic capture is calculated with the option “Best signal level per HCS layer” meaning that there is an overlap between HCS layers service areas. Let denote this area (TCH service area of the macro layer overlapped by the TCH service area of the micro layer). Traffic on the overlapping area is distributed to the TCH subcell of the micro layer because it has a higher priority. On this area, traffic of the micro layer may overflow to the macro layer. In this case, the traffic demand is the same on the TCH subcell of the micro layer but increases on the TCH subcell of the macro layer.

Atoll evaluates the traffic demand on the micro layer (higher priority) as explained above. For further details, please refer to formulas for normal cells. Then, it proceeds with the macro layer (lower priority).

p_{up c t}___

D_{up c t}__ _{ m}_

D_{up c t}___{ m}_ Txi,TCH_INNER = X_{up m}_ Txi,TCH_INNER p _{up c t}_ __

D_{up c t}___{ m}_ Txi,TCH = X_{up m}_ Txi,TCH p _{up c t}_ __+D_{up c t}___{ m}_ Txi,TCH_INNER O _maxTxi,TCH_INNER O_maxTxi,TCH_INNER

p_{up p t}_ __

D_{up p t}__ _{ m}_

D_{up p t}__ _{ m}_ Txi,TCH_INNER = X_{up m}_ Txi,TCH_INNER p _{up p t}_ __

D_{up p t}__ _{ m}_ Txi,TCH = X_{up m}_ Txi,TCH p _{up p t}_ __+D_{up p t}__ _{ m}_ Txi,TCH_INNER O _maxTxi,TCH_INNER O_maxTxi,TCH_INNER

p_{up p t}_ __

D_{up p t}__ _{ m}_

D_{up p t}__ _{ m}_ Txi,TCH_INNER = X_{up m}_ Txi,TCH_INNER p _{up p t}_ __

Note:

• Traffic overflowing to the macro layer is not uniformly spread over the TCH service area of Txj. It is only located on the overlapping area.

Figure 5.5Representation of Micro and Macro Layers

Soverlapping macro

Txj TCH

 

Number of subscribers ( ) for each TCH subcell (Txj, TCH) of the macro layer, per user profile up with the mobility m, is inferred as:

Where is the TCH service area of Txj containing the user profile up with the mobility m and D is the profile density.

For each user described in the user profile up with the circuit switched service c and the terminal t, the probability for the user being connected ( ) is calculated as explained in "Circuit Switched Services" on page 156.

Then, Atoll evaluates the traffic demand, , in Erlangs in the subcell (Txj, TCH) service area.

For each user described in the user profile up with the packet switched service p and the terminal t, probability for the user to be connected ( ) is calculated as explained in "Packet Switched Services" on page 157.

Then, Atoll evaluates the traffic demand, , in kbits/s in the subcell (Txj, TCH) service area.

Where is the maximum rate of traffic overflow (stated in %) specified for the TCH subcell of Txi (micro

layer) and is the TCH service area of Txi containing the user profile up with the mobility m.

Concentric Cells

Atoll evaluates the traffic demand on the micro layer (higher priority HCS layer) as explained above. For further details, please refer to formulas given in case of concentric cells. Then, it proceeds with the macro layer (lower priority HCS layer).

The traffic capture is calculated with the option “Best signal level per HCS layer”. It means that there are overlapping areas between HCS layers where traffic is spread according to the layer priority. On these areas, traffic of the higher priority layer may overflow.

The TCH_INNER service area of the macro layer is overlapped by the micro layer. This area consists of two parts: an area

overlapped by the TCH service area of the micro layer and another overlapped

by the TCH_INNER service area of the micro layer .

Let us consider three areas, S₁, S₂ and S₃.

Soverlapping–Txi,TCH_INNER macro

Where is the TCH_INNER subcell service area of Txj containing the user profile up with the mobility m. We only consider the overlapping areas containing the user profile up with the mobility m.

On S₁, the number of subscribers per user profile up with a given mobility m ( ) is inferred:

Where D is the user profile density.

The traffic spread over the TCH_INNER service area of the micro layer may overflow on the TCH subcell. The traffic overflowing to the TCH subcell is located on the TCH_INNER service area. On S₂, the TCH subcell traffic coming from the TCH_INNER subcell traffic overflow may overflow proportional to R₂.

The traffic spread over the ring served by the TCH subcell of the micro layer only may overflow on S₃ proportional to R₃.

Where and are the TCH and TCH_INNER service areas of Txi respectively

containing the user profile up with the mobility m.

For each user described in the user profile up with a circuit switched service c and a terminal t, the probability for the user being connected ( ) is calculated as explained in "Circuit Switched Services" on page 156. Then, Atoll evaluates the traffic demand, , in Erlangs in the subcell (Txj, TCH_INNER) service area.

For each user described in the user profile up with a packet switched service p and a terminal t, probability for the user to be connected ( ) is calculated as explained in "Packet Switched Services" on page 157.

Then, Atoll evaluates the traffic demand, , stated in kbits/s in the subcell (Txj, TCH_INNER) service area.

Where and are the maximum rates of traffic overflow (stated in %) specified for the TCH and TCH_INNER subcells of Txi respectively.

The area of the TCH ring of the macro layer is overlapped by the micro layer. There are two parts: an area overlapped by

the TCH service area of the micro layer and another one by the

TCH_INNER service area of the micro layer .

Let us consider three areas, S’₁, S’₂ and S’₃.

Where and are the TCH and TCH_INNER subcell service areas of Txj

respectively. We only consider the overlapping areas containing the user profile up with the mobility m.

On S’₁, the number of subscribers per user profile up with a given mobility m ( ) is inferred:

Where D is the user profile density.

S_{up m}^macro_ Txj,TCH_INNER

Soverlapping–Txi,TCH_INNER macro

The traffic spread over the TCH_INNER service area of the micro layer may overflow on the TCH subcell. The traffic overflowing on the TCH subcell is located on the TCH_INNER service area. On S’₂, the TCH subcell traffic coming from the TCH_INNER subcell traffic overflow may overflow proportionally to R’₂.

The traffic spread over the ring served by the TCH subcell of the micro layer only may overflow on S’₃ proportional to R’₃.

Where and are the TCH and TCH_INNER service areas of Txi respectively

containing the user profile up with the mobility m.

Then, Atoll evaluates the traffic demand, , in Erlangs in the subcell (Txj, TCH) service area.

For each user described in the user profile up with a packet switched service p and a terminal t, the probability for the user being connected ( ) is calculated as explained in "Packet Switched Services" on page 157.

Then, Atoll evaluates the traffic demand, , in kbits/s in the subcell (Txj, TCH) service area.

Where is the maximum rate of traffic overflow (stated in %) specified for the TCH subcell of Txi (micro layer), the maximum rate of traffic overflow indicated for the TCH_INNER subcell of Txi (macro layer), the maximum rate of traffic overflow indicated for the TCH_INNER subcell of Txj (macro layer) and the number of subscribers with the user profile up and mobility m on the TCH service area of Txi (as explained in "Concentric Cells" on page 157).

5.5.2.2 Sector Traffic Maps

We assume that the traffic map is built from a coverage by transmitter prediction calculated for the TCH subcells with options:

• “HCS Servers” and no margin if the network only consists of normal cells and concentric cells,

• “Highest Priority HCS Server” and no margin in case of HCS layers.

When creating the traffic map, you have to specify the traffic demand per transmitter and per service (throughput for a max rate packet switched service and Erlangs for a circuit switched or constant bit rate packet switched service) and the global distribution of terminals and mobility types.

Let denote the Erlangs for the circuit switched service, c, on the TCH subcell of Txi.

Let denote the throughput of the packet switched service (Max Bit Rate), p, on the TCH subcell of Txi.

Let denote the Erlangs for the packet switched service (Constant Bit Rate), p, on the TCH subcell of Txi.

We assume that 100% of users have the terminal, t, and the mobility type, m.

5.5.2.2.1 Normal Cells (Nonconcentric, No HCS Layer)

For each circuit switched service, c, Atoll evaluates the traffic demand, D_c,t,m, in Erlangs in the subcell (Txi, TCH) service area.

R'₂ S'₂

S_{up m}^micro_ Txi,TCH_INNER

---=

R'₃ S'₃

S_{up m}^micro_ Txi,TCH S– _{up m}^micro_ Txi,TCH_INNER

---=

S_{up m}^micro_ Txi,TCH S_{up m}^micro_ Txi,TCH_INNER

p_{up c t}___

D_{up c t}^macro___{ m}_

D_{up c t}^macro__ _{ m}_ Txj TCH 

X_{up m}^macro_ Txj TCH  p _{up c t}___+

D_{up c t}^macro__ _{ m}_ Txj,TCH_INNER O _maxTxj,TCH_INNER+

R'₂D_{up c t}^micro__ _{ m}_ Txi,TCH_INNERO_maxTxi,TCH_INNERO_maxTxi,TCH+ R'₃X_{up m}^micro_ Txi TCH p_{up c t}___{ m}_ O_maxTxi TCH 

p_{up p t}__ _

D_{up p t}^macro__ _{ m}_

D_{up p t}^macro_ _ _{ m}_ Txj TCH 

X_{up m}^macro_ Txj TCH  p _{up p t}_ __+

D_{up p t}^macro_ _ _{ m}_ Txj,TCH_INNER O _maxTxj,TCH_INNER+

R'₂D_{up p t}^micro_ _ _{ m}_ Txi,TCH_INNERO_maxTxi,TCH_INNERO_maxTxi,TCH+ R'₃X_{up m}^micro_ Txi TCH p_{up p t}_ __{ m}_ O_maxTxi TCH 

O_maxTxi,TCH O_maxTxi,TCH_INNER O_maxTxj,TCH_INNER X_{up m}^micro_ Txi TCH 

E_cTxi TCH  T_pTxi TCH  E_pTxi TCH 

D_{c t m}_{ } Txi TCH  = E_cTxi TCH 

For each packet switched service (Max Bit Rate), p, Atoll evaluates the traffic demand, D_p,t,m, in kbits/s in the subcell (Txi, TCH) service area.

For each packet switched service (Constant Bit Rate), p, Atoll evaluates the traffic demand, D_p,t,m, in kbits/s in the subcell (Txi, TCH) service area.

where is the guaranteed bit rate of the constant bit rate packet switched service p.

5.5.2.2.2 Concentric Cells

In case of concentric cells, Atoll distributes a part of traffic on the TCH_INNER service area (TCH_INNER is the highest priority traffic carrier) and the remaining traffic, on the ring served by the TCH subcell only. The traffic spread over the TCH_INNER subcell may overflow to the TCH subcell. In this case, the traffic demand is the same on the TCH_INNER subcell and rises on the TCH subcell.

For each circuit switched service, c, Atoll evaluates the traffic demand, D_c,t,m, in Erlangs in the subcell, (Txi, TCH_INNER) and (Txi, TCH), service areas.

and

For each packet switched service (Max Bit Rate), p, Atoll evaluates the traffic demand, D_p,t,m, in kbits/s in the subcell, (Txi, TCH_INNER) and (Txi, TCH), service areas.

and

Where is the maximum rate of traffic overflow (stated in %) specified for the TCH_INNER subcell, and are the TCH and TCH_INNER service areas of Txi respectively.

For each packet switched service (Constant Bit Rate), p, Atoll evaluates the traffic demand, D_p,t,m, in kbits/s in the subcell, (Txi, TCH_INNER) and (Txi, TCH), service areas.

and

Where is the maximum rate of traffic overflow (stated in %) specified for the TCH_INNER subcell, and are the TCH and TCH_INNER service areas of Txi respectively.

5.5.2.2.3 HCS Layers

We assume we have two HCS layers: the micro layer has a higher priority and the macro layer has a lower one. Txi belongs to the micro layer and Txj to the macro one. The traffic contained in the input traffic map can be assigned to all the HCS layers.

Atoll distributes traffic on the TCH service areas. The traffic capture is calculated with the option “HCS Servers”. It means that there is an overlapping area between HCS layers. Let denote the TCH service area of the macro layer overlapped by the TCH service area of the micro layer. Traffic on the overlapping area is distributed to the

D_{p t m}_{ } Txi TCH  = T_pTxi TCH 

D_{p t m}_{ } Txi TCH  = E_pTxi TCH  TP _{p GBR}_ TP_{p GBR}_

Note:

• Traffic overflowing from the TCH_INNER to the TCH is not uniformly spread over the TCH service area. It is only located on the TCH_INNER service area.

D_{c t m}_{ } Txi,TCH_INNER S Txi,TCH_INNER 

O_maxTxi,TCH_INNER S Txi,TCH  S Txi,TCH_INNER 

Soverlapping macro

Txj TCH

 

TCH subcell of the micro layer (higher priority layer). On this area, traffic of the micro layer may overflow to the macro layer.

In this case, the traffic demand is the same on the TCH subcell of the micro layer but rises on the TCH subcell of the macro layer.

Atoll starts evaluating the traffic demand on the micro layer (highest priority HCS layer).

For each circuit switched service, c, Atoll calculates the traffic demand, , in Erlangs in the subcell (Txi, TCH) service area.

For each packet switched service (Max Bit Rate), p, Atoll calculates the traffic demand, , in kbits/s in the subcell (Txi, TCH) service area.

For each packet switched service (Constant Bit Rate), p, Atoll calculates the traffic demand, , in kbits/s in the subcell (Txi, TCH) service area.

Then, Atoll proceeds with the macro layer (lower priority HCS layer).

For each circuit switched service, c, Atoll calculates the traffic demand, , in Erlangs in the subcell (Txj, TCH) service area.

For each packet switched service (Max Bit Rate), p, Atoll calculates the traffic demand, , in kbits/s in the subcell (Txj, TCH) service area.

Where is the maximum rate of traffic overflow (in %) specified for the TCH subcell of Txi (micro cell) and the TCH service area of Txi.

For each packet switched service (Constant Bit Rate), p, Atoll calculates the traffic demand, , in kbits/s in the subcell (Txj, TCH) service area.

Where is the maximum rate of traffic overflow (in %) specified for the TCH subcell of Txi (micro cell) and the TCH service area of Txi.

Concentric Cells

Atoll evaluates the traffic demand on the micro layer as explained above in case of concentric cells and then proceeds with the macro layer (lower priority layer).

The traffic capture is calculated with the option “HCS Servers”. It means that there is overlapping areas between HCS layers where traffic is spread over according to the layer priority. On these areas, traffic of the higher priority layer may overflow.

Note:

• Traffic overflowing on the macro layer is not uniformly spread over the TCH service area of Txj. It is only located on the overlapping area.

Note:

• You can restrict the traffic assignement of each traffic map to a specific HCS layer in the running options of the traffic capture. If you do so, no overflow occurs between HCS layers and the only overflow which is considered occurs within concentric cells (See "Concentric Cells" on page 157).

The TCH_INNER service area of the macro layer is overlapped by the micro layer. This area consists of two parts: an area

overlapped by the TCH service area of the micro layer and another overlapped

by the TCH_INNER service area of the micro layer .

Let us consider three areas, S₁, S₂ and S₃.

Where is the TCH_INNER subcell service area of Txj.

The traffic specified for Txj in the map description ( ) is spread over S₁ proportionally to R₁.

is the TCH service area of Txj in the traffic map with the option “Best signal level of the highest priority layer”.

The traffic spread over the TCH_INNER service area of the micro layer may overflow to the TCH subcell. The traffic overflowing to the TCH subcell is located on the TCH_INNER service area. On S₂, the TCH subcell traffic coming from the TCH_INNER subcell traffic overflow may overflow proportional to R₂.

The traffic spread over the ring only served by the TCH subcell of the micro layer may overflow on S₃ proportional to R₃.

For each circuit switched service, c, Atoll calculates the traffic demand, , in Erlangs in the subcell (Txj, TCH_INNER) service area.

For each packet switched service (Max Bit Rate), p, Atoll calculates the traffic demand, , in kbits/s in the subcell (Txj, TCH_INNER) service area.

Soverlapping–Txi,TCH_INNER macro

S₂ Soverlapping–Txi,TCH_INNER macro

S^macroTxj,TCH_INNER

E_cTxj TCH 

S^microTxi,TCH_INNER

Where is the maximum rate of traffic overflow (stated in %) specified for the TCH subcell of Txi, is the maximum rate of traffic overflow (stated in %) specified for the TCH_INNER subcell of Txi and is the TCH subcell service area of Txi.

For each packet switched service (Constant Bit Rate), p, Atoll calculates the traffic demand, , in kbits/s in the subcell (Txj, TCH_INNER) service area.

The area of the TCH ring of the macro layer is overlapped by the micro layer. There are two parts: an area overlapped by

the TCH service area of the micro layer and another overlapped by the

TCH_INNER service area of the micro layer .

Let us consider three areas, S’₁, S’₂ and S’₃.

Where and are the TCH and TCH_INNER subcell service areas of Txj

respectively.

The traffic specified for Txj in the map description ( ) is spread over S’₁ proportional to R’₁.

is the TCH service area of Txj in the traffic map with the option “Best signal level of the highest priority layer”.

The traffic spread over the TCH_INNER service area of the micro layer may overflow to the TCH subcell. The traffic overflowing to the TCH subcell is located on the TCH_INNER service area. On S’₂, the TCH subcell traffic coming from the TCH_INNER subcell traffic overflow may overflow proportional to R’₂.

The traffic spread over the ring only served by the TCH subcell of the micro layer may overflow on S’₃ proportional to R’₃.

For each circuit switched service, c, Atoll calculates the traffic demand, , in Erlangs in the subcell (Txj, TCH) service area. O_maxTxi,TCH_INNER

S^microTxi TCH  O_maxTxi,TCH_INNER

S^microTxi TCH 

Soverlapping–Txi TCH  macro

Txj,TCH -- TCH_INNER

 

Soverlapping–Txi,TCH_INNER macro

S'₂ Soverlapping–Txi,TCH_INNER macro

S^microTxi,TCH_INNER

For each packet switched service (Max Bit Rate), p,Atoll calculates the traffic demand, , in kbits/s in the subcell (Txj, TCH) service area.

Where is the maximum rate of traffic overflow (stated in %) specified for the TCH_INNER subcell of Txj, is the maximum rate of traffic overflow (stated in %) specified for the TCH subcell of Txi, is the maximum rate of traffic overflow (stated in %) specified for the TCH_INNER subcell of Txi, is the TCH subcell service area of Txi and is the TCH_INNER subcell service area of Txi.

For each packet switched service (Constant Bit Rate), p,Atoll calculates the traffic demand, , in kbits/s in the subcell (Txj, TCH) service area.

5.6 Network Dimensioning

Atoll is capable of dimensioning a GSM GPRS EDGE network with a mixture of circuit and package switched services.

This section describes the technical details of Atoll’s dimensioning engine.

5.6.1 Dimensioning Models and Quality Graphs

In Atoll, a dimensioning model is an entity utilized by the dimensioning engine along with other inputs (traffic, limitations, criteria, etc.) in the process of dimensioning. A dimensioning model defines the QoS KPIs to be taken into account when dimensioning a network for both circuit and packet switched traffic. The user can define either to use Erlang B or Erlang

In document Atoll 2.8.3 RF Technical Reference Guide E2 (Page 159-168)