BINARY-TREE MULTIPLEXING SCHEDULING

Abstract

Multiplexed scheduling of information blocks from multiple sources on a single communication channel divided into multiple address positions is performed. The information block from each source has a repetition period and is divided into a number of segments. A bandwidth adequacy verification is performed for expected information blocks to be scheduled on the channel. Mapping positions are assigned corresponding to nodes in a binary tree, whereby each layer of the binary tree corresponds to a repetition period of the respective information block. Assignment of the information blocks to the binary tree is based on a priority order of repetition period of the respective information block.

Description

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

In wireless communications, there may be multiple blocks of information from multiple sources required to be scheduled for periodic access of single channel. Due to constraints of the physical layer of the channel, such as limited transmission rate or power level, each block of information may need to be segmented into several segments, with each segment scheduled at a position for accessing the channel.

While scheduling the different sources of information, several requirements must be considered. The single channel is divided into multiple addresses or positions to which information segments are assigned or scheduled. As multiple sources of information have their associated information block segments scheduled along the channel positions, the scheduled information is considered multiplexed onto the channel. Therefore, conflicts of positions between different segments of information must be avoided, i.e., a channel position cannot be shared by segments of two different information blocks. Thus, the first requirement is that each position can be assigned to only one segment of information.

Second, since the repetition period required by each source of information is based on functions associated with the information, the different sources of information require different periods for accessing a single channel. For example, in 3G UMTS, a Broadcast Channel (BCCH) having System Information Blocks (SIBs) with different periods signifies various latency of system functions, such as Power Control or Cell Selection. Shorter repetition periods lead to shorter latency since User Equipment (UE) can receive system information faster than required to perform system functions. However, this requirement compromises efficient use of limited bandwidth of the channel. Shorter repetition periods also imply heavier loading to the single channel and limit the possibility to allocate the bandwidth for other usages.

Third, in order to maximize channel efficiency, unassigned positions on the channel should be kept to a minimum in order to maximize the utilization of the channel.

Fourth, segments of the same block of information should be scheduled as consecutively as possible, since information often cannot be read until all segments of the same source of information arrive at the receiver.

One solution to this problem has been to use a first come first service (FCFS) assignment method. In this method, the scheduler begins scheduling with a first source's block of information. Once the first source of information is scheduled, the scheduler then assigns positions to the block of information of a second source of information on to the single channel. While scheduling the second source of information, the scheduler needs to avoid assigning channel positions that are already assigned to the first source's block of information. Thus, while scheduling the subsequently scheduled blocks of information, the scheduler needs to keep track of all positions that are already assigned to previously scheduled blocks of information.

FIGS. 1A and 1B show an example in which three sources of information are scheduled to access a single channel, CHANNEL A. Three blocks of information, SOURCE 1, SOURCE 2, and SOURCE 3 are shown having varying segment counts and repetition periods. FIG. 1B shows the scheduling of the red, blue and green information segments to positions on CHANNEL A based on the segment counts and required repetition periods of SOURCE 1, SOURCE 2 and SOURCE 3. As evident in CHANNEL A shown in FIG. 1B, there are unassigned positions remaining after the scheduling of the SOURCE 1, SOURCE 2 and SOURCE 3 information blocks (8, 9, 18, 19, 20 . . . ). As more blocks of information with different segment count and repetition period constraints are added for scheduling on CHANNEL A, a scheduling method that does not compromise one or more of the above requirements becomes difficult to achieve.

Using the FCFS approach results in several compromises, such as segments belonging to the same source's block of information cannot be scheduled consecutively since the solution does not reserve enough consecutive positions available that can satisfy information with large segment counts. This compromise is shown in FIG. 1B for SOURCE 3, as the green information segments are not scheduled consecutively on CHANNEL A. This delays the reading of the SOURCE 3 block of information as the receiver awaits for all segments of the information block to arrive. Also, due to the periodic nature of the scheduling, two sources of information may conflict with each other at some future position, thus creating the need to perform global searches each time an information segment is to be assigned to a position in order to avoid the possible conflict.

What is needed is a method and system that determines the required bandwidth for a given set of information blocks and that efficiently schedules information while optimizing for the above requirements.

SUMMARY

A method for multiplexed scheduling of information blocks from multiple sources on a single communication channel divided into multiple address positions is disclosed. The information block from each source has a repetition period and is divided into a number of segments. Once the total number of positions on the channel to be scheduled is determined, positions are mapped in a non-sequential order corresponding to nodes in a binary tree, whereby each layer of the binary tree corresponds to a particular repetition period. The blocks of information are assigned in the order of ascending repetition period. The information segments of each block are scheduled to unassigned positions at the associated binary tree layer as well as to all corresponding child nodes.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings.

FIGS. 1A and 1B show prior art multiplexing of three different blocks of information onto a single channel;

FIG. 2 shows a four layer binary tree;

FIGS. 3A and 3B show a method flow diagram for scheduling multiple sources of information on a multiplexed single channel using a binary tree.

FIG. 4 shows a sample of multiple blocks of information from information sources to be scheduled on a multiplexed single channel.

FIGS. 5A through 5H show the progression of mapping the FIG. 4 information blocks to assigned positions onto a binary tree.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment.

R blocks of information denoted by INFO₁, INFO₂, . . . , INFO_R, each associated with a source of information are introduced herein. Each information block INFO has its own repetition period RP, which indicates how often the information should access the single channel, and is divided into segments SEGs with a segment count SC, which is the number of segments SEGs to a block of information. A single channel is divided into address positions P to which information segments SEGs are scheduled or assigned.

The following formula determines whether there is adequate bandwidth for a given set of information sources to be accessed by a single channel.

$\begin{array}{cc}\sum _{r=1}^R\frac{{\mathrm{INFO}}_r\left(\mathrm{SC}\right)}{{\mathrm{INFO}}_r\left(\mathrm{RP}\right)}\le 1& \left(\mathrm{Equation}1\right)\end{array}$

Adequate bandwidth exists if Equation 1 holds true.

FIG. 2 shows an example of a binary tree with N layers and 2^N positions on the bottom layer. N is chosen such that 2^N is the maximum repetition period RP among all of the information blocks INFOs. The repetition period RP usually depends on overall system requirements, and is preferred to be equivalent to 2^N for some natural number N. This avoids conflict of different information blocks INFOs at any particular position.

Returning to FIG. 2, each node of the layer n where n≦N, can be represented as an n-dimension vector (a_n, a_n-1, . . . , a₁) with arguments 0 or 1. A binary tree is defined such that at each layer, the argument an alternates between 0 and 1 from left to right. Each node of the layer n is associated with a value that is equivalent to the binary representation of the vector. For example, at node A with layer value n=4, a vector (a₄, a₃, a₂, a₁) has a binary representation of (1011), which is equivalent to eleven (11). For the binary tree shown in FIG. 2 with four layers (N=4), there are sixteen positions (2⁴) in the order 0, 8, 4, 12, 2, . . . 7, 15, as shown in the bottom row. Each node has an associated parent node and two child nodes.

FIG. 3 shows a flow diagram of a method 150 for scheduling multiple blocks of information onto a single communication channel. First, adequate bandwidth is confirmed for the given set of information blocks using Equation 1 (step 100). Next, the scheduler must determine the number of positions necessary to allow all information segments to be scheduled (step 101). P_MAX represents the maximum number of positions needed to allow the total number of segments to be scheduled, and is represented as follows:

P _MAX=2^N−1  (Equation 2)

where N=log₂(maxINFO_r(RP))  (Equation 3)

For each information block INFO, positions P(i) for i=(0, 1, . . . , SC) are selected from among the positions from P=0 to P=2^N−1.

Next, in step 102, an information list, LIST A, is created for all of the information blocks INFOs sorted in ascending order of their repetition periods RP. Some systems might require specific positions for a certain type of information. For instance, when the block of information INFO is control information, such as a management information base (MIB), it is considered to be a header INFO, and is placed on the top of LIST A. When sorting the information blocks INFOs in LIST A, the non-header INFOs are sorted in ascending order of RP, directly below the header INFO in LIST A. The scheduler refers to LIST A for the order in which to assign information segments onto the single channel. Using the format as shown in FIG. 2, a binary tree is created with N layers and 0 to 2^N−1 positions (step 103). A position assignment list, LIST B, is next created in step 104, where each information segment SEG for each information block INFO is assigned to a single position P. The next step for scheduling, step 105, involves determining which layer of the binary tree is to be used for the first information block INFO₁. For layer m, m is defined by Equation 4:

m=log₂(INFO₁(RP))≦N  Equation 4

In step 106, positions for the first information block INFO₁ are chosen using consecutive numbers from P=0 to P=(SC−1). Nodes on the m layer that represent assigned positions for the first information block INFO₁, are virtually marked on the binary tree in step 107. All child nodes below the virtually marked nodes on the m layer are also marked as assigned and are removed from consideration for assigning positions to any segment SEG of the remaining information blocks INFOs. In step 108, the next INFO is retrieved from LIST A. Layer k represents a layer for any subsequently scheduled information block INFO_r, and is defined by Equation 5:

k=log₂(INFO_r(RP))≦N  Equation 5

Two criteria are examined in step 109 when assigning information segments SEGs of INFO to positions P: 1) whether INFO immediately proceeds the header INFO (i.e., INFO is the first non-header INFO in LIST A); and 2) whether k<m. If both criteria of step 109 are satisfied, then INFO SEGs are assigned in step 111 to available positions P in the k layer having the greatest numerical value and with the smallest possible range among the available positions P from P(0) to P (SC−1). Otherwise, if the step 109 criteria are not satisfied, then INFO SEGs are assigned to positions P on layer k with the least numerical values and the smallest possible range among the available positions P (step 110).

In step 112, all assigned P nodes are virtually marked and, as in step 107, all nodes below the marked P nodes on the k layer are marked as assigned and are removed from consideration for the remaining INFOs. Finally, steps 108 through 112 are repeated until all information blocks INFOs are scheduled (step 113).

An example is shown in FIG. 4 having eleven information blocks (MIB, INFO1-INFO10), each with its own segment count SC and repetition period RP. Using Equation 1, a check for adequate bandwidth in step 100 is performed as follows:

$\begin{array}{c}\frac{5}{16}+\frac{2}{32}+3\left(\frac{1}{32}\right)+2\left(\frac{10}{128}\right)+\frac{1}{32}+2\left(\frac{5}{64}\right)+\frac{1}{8}\le 1\\ 0.9375\le 1\end{array}$

Thus, there is adequate bandwidth and the utilization of the broadcast channel is 93.75%.

The maximum repetition period RP among the eleven information blocks is 128, corresponding with INFO5 and INFO6 of FIG. 4. Using Equation 3, it follows that N=7. Therefore, positions P for scheduling on the broadcast channel will range between 0 and 127, in accordance with Equation 2 (step 101). The non header blocks INFO1-INFO10 information are then rearranged in ascending order of RP (step 102), as shown in Table 1. Since the management information base MIB is the header INFO and contains control information for the communication system to which the information blocks are received, the first segment of MIB is to be assigned at P=0 so that this information is read first by the receiver. Thus, MIB is in the first row of LIST A in Table 1 regardless that the RP for MIB is not the least among the information blocks.

TABLE 1
LIST A
	Information	Segment Count	Repetition Period	Layer
	Block	SC	RP	Value
	MIB	5	16	4
	INFO10	1	8	3
	INFO1	2	32	5
	INFO4	1	32	5
	INFO7	1	32	5
	INFO3	1	32	5
	INFO2	1	32	5
	INFO9	5	64	6
	INFO8	5	64	6
	INFO5	10	128	7
	INFO6	10	128	7

With the number layers established as N=7, a binary tree with seven layers and positions from P=0 to P=127 is created (step (103) as shown in FIG. 5A. In order to track the assigned positions P(i) for each information block, LIST B is generated as the position assignment list (step 104). Using Equation 4, the layer value for information block MIB is calculated (step 105):

$\begin{array}{c}m={\log }_2\left({\mathrm{INFO}}_1\left(\mathrm{RP}\right)\right)\\ ={\log }_2\left(16\right)\\ =4\end{array}$

The five segments of MIB are then assigned (step 106) to consecutive positions P=0, 1, 2, 3, 4 for positions P(0) to P(4) as shown in Table 2. As each information segment is scheduled for an information block INFO, the corresponding position P is recorded in LIST B.

TABLE 2
LIST B
Information											P
Block	P(0)	P(1)	P(2)	P(3)	P(4)	P(5)	P(6)	P(7)	P(8)	P(9)	Range
MIB	0	1	2	3	4						5
INFO10
INFO1
INFO4
INFO7
INFO3
INFO2
INFO9
INFO8
INFO5
INFO6

Referring to the binary tree of FIG. 5B, all nodes below layer 4 for P=0, 1, 2, 3 and 4, are eliminated as potentially assignable positions for the remaining segments of information (step 107). For example, at NODE B on layer 4 where P=0, the following nodes are eliminated and will not contain segments of information: the two nodes at layer 5 (P=0, 16), the four nodes at layer 6 (P=0, 32, 16, 48) and the eight nodes at layer 7 (P=0, 64, 32, 96, 16, 80, 48, 112). The shaded area under NODE B in FIG. 5B shows the elimination of these child nodes. Similarly, the child nodes associated with P=1, 2, 3, 4 are marked as assigned, as shown by the shaded areas below layer 4 in FIG. 5B.

The next block of information to be scheduled is INFO10 since it directly follows MIB in LIST A (step 108). Based on Equation 5, the layer k value for INFO10 is k=3. Looking on the binary tree of FIG. 5B at layer k=3, the possible candidates for selection are P=5, 6 or 7, since P=0 through P=4 were assigned to MIB. The largest of these, position P=7, shown as NODE C in FIG. 5C, is chosen according to steps 109 and 111 since k=m and INFO10 is the first non-header INFO in LIST A. The shaded area under NODE C shows the elimination of all child nodes for P=7 at layer k=3 (step 112).

With INFO10 scheduled, LIST A is consulted for the next information block for scheduling. As shown on Table 1, INFO1 is next in line for scheduling. The layer value k=5 associated with INFO1 is calculated from Equation 5 (step 108). Referring to FIG. 5C, the available nodes at layer 5 are those that have not been eliminated by the scheduling of INFO blocks MIB and INFO10. With the first non-header INFO scheduled, all remaining INFOs are scheduled to positions with the least numerical values and as consecutive to one another as possible according to steps 109 and 110. Therefore, the two segments for INFO1 are assigned to positions P=5, 6 as shown in FIG. 5D.

Repeating steps 108,109, 110 and 112, information blocks INFO4 and INFO7 are scheduled next in accordance with the order shown in LIST A. Similar to INFO1, information blocks INFO4 and INFO7 have a layer value of k=5, and thus the next available consecutive positions P=8 and P=9 are assigned to INFO4 and INFO7 respectively. The marking of these positions is shown in FIG. 5E

Information blocks INFO2 and INFO3 have identical repetition periods RP of 32 and a layer value of k=5 accordingly. Consulting FIG. 5E, positions P=10, 11 are available at layer 5 and are chosen as shown in FIG. 5F.

The next information block shown in LIST A for scheduling is INFO9, which has a layer value of k=6. The five information segments of INFO9 are scheduled at the five consecutive positions available at layer 6 with the least numerical values, which are P=24, 25, 26, 27, 28. These positions are recorded in LIST B and the positions that fall below these nodes in layer 7 are eliminated from future consideration as shown in FIG. 5G. Similarly, information block INFO8 has five segments of information and is associated with layer 6. Searching the remaining available positions at layer 6 for five consecutive positions yields P=56, 57, 58, 59, 60. These positions are recorded in LIST B and the corresponding child positions in layer 7 are eliminated from consideration (FIG. 5G) as with the previous information blocks. The remaining information blocks, INFO5 and INFO6, have layer values of k=7 and ten segments of information. Turning to FIG. 5H, ten positions are chosen for INFO5 segments from the remaining available positions at layer 7 which have the smallest range possible: P=12, 13, 14, 21, 22, 29, 30, 44, 45, 46. Similarly, INFO6 segments are scheduled to positions that are available at layer 7 and are recorded in LIST B as shown in Table 3, which shows the completed LIST B for system 10.

TABLE 3
LIST B
Information											P
Block	P(0)	P(1)	P(2)	P(3)	P(4)	P(5)	P(6)	P(7)	P(8)	P(9)	Range
MIB	0	1	2	3	4						5
INFO10	7										1
INFO1	5	6									2
INFO4	8										1
INFO7	9										1
INFO3	10										1
INFO2	11										1
INFO9	24	25	26	27	28						5
INFO8	56	57	58	59	60						5
INFO5	12	13	14	21	22	29	30	44	45	46	34
INFO6	76	77	78	85	86	93	94	108	109	110	34

The last column of Table 3 shows the P range for each information block. For information blocks INFO5 and INFO6 with ten segments of information each, the range of position values is 34. This shows that out of 128 positions, the complete set of information segments for INFO5 and INFO6 is received optimized, as the segments are assigned to a group of positions that are relatively compact along the single channel. Thus, the receiver can read INFO5 and INFO6 more quickly and efficiently than if their information segments had been spread over a greater range along the 128 available positions. All other information blocks INFOs have a P range exactly equivalent to the segment count SC, which is the maximum possible efficiency.

To one skilled in the art, it would be evident that the method disclosed herein may be implemented by a microprocessor with memory. The binary tree mapping can reside in memory. As segments of information are scheduled, the microprocessor updates the mapping to reflect that information segments are assigned to their respective positions in the corresponding binary tree layer as well as all corresponding child node positions.

It should also be recognized to one skilled in the art that a B-tree or splay tree could similarly be mapped in accordance with the method disclosed herein.

Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. The methods or flow charts provided herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).

Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine.

A processor in association with software may be used to implement a radio frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB) module.

Claims

1. A method for multiplexed scheduling of information blocks from multiple sources on a single communication channel, comprising: defining blocks of information and associating each block of information with a source of information;dividing the single communication channel into multiple address positions;confirming bandwidth for the defined blocks of information;determining a number of positions necessary to allow the information blocks to be scheduled;sorting the information blocks in a scheduler list; andscheduling the information blocks in accordance with the scheduling list.

2. The method as in claim 1, wherein each information block has its own repetition period.

3. The method as in claim 2, wherein the information blocks are sorted in ascending order of their repetition period.

4. The method as in claim 2, further comprising dividing information blocks into information segments.

5. The method as in claim 2, wherein the repetition period indicates how often the information accesses a single channel.

6. The method as in claim 1, wherein information segments are assigned to the multiple address positions corresponding to binary tree nodes.

7. The method as in claim 6, further comprising creating a position assignment list where each information segment for each information block is assigned to a single position.

8. The method as in claim 6 wherein a first information block is assigned to nodes of the binary tree in accordance with the following equation: m=log2(INFO1(RP))≦N wherein m represents a binary tree layer, (INFO1(RP)) represents a first information block repetition period, and N is the total number of binary tree layers.

9. The method as in claim 8, wherein the first information block is a management information base (MIB).

10. A microprocessor configured to define blocks of information and to associate each block of information with a source of information; divide the single communication channel into multiple address positions; confirm bandwidth for the defined blocks of information; determine a number of positions necessary to allow the information blocks to be scheduled; sort the information blocks in a scheduler list; and schedule the information blocks in accordance with the scheduling list.

11. The microprocessor as in claim 10, configured to sort the information blocks in ascending order by repetition period, where each information block has its own repetition period according to how often the information accesses the communication channel.

12. The microprocessor as in claim 11, configured to divide each information blocks into information segments.

13. The microprocessor as in claim 12, wherein the information segments are assigned to the multiple address positions corresponding to binary tree nodes.

14. The microprocessor as in claim 13, further configured to create a position assignment list where each information segment for each information block is assigned to a single position.

15. The microprocessor as in claim 13, further configured to assign a first information block to nodes of the binary tree in accordance with the following equation: m=log2(INFO1(RP))≦N wherein m represents a binary tree layer, (INFO1(RP)) represents a first information block repetition period, and N is the total number of binary tree layers.

16. The microprocessor as in claim 15, wherein the first information block is a management information base (MIB).